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vendored
lodash.once
v4.1.1
MIT

once

The standalone lodash.once package as a vendorable file. Useful when you want a small but exact once-only invocation contract without another dependency.

Why copy this?

This page ships the published lodash.once file in both raw and normalized forms. The point is to vendor the exact one-time invocation behavior instead of rewriting it case by case.

Native alternative: A closure can implement a one-time call quickly, but teams often still prefer keeping a known utility contract instead of rewriting it repeatedly.

Note: Raw and normalized views are both available. Use normalized when you want an ESM and TypeScript-friendly file, and raw when you want the original published package shape.

This copy is your responsibility once you adopt it. It does not automatically receive upstream bug fixes or security updates.

Snippet
Copy-first distribution
Normalized
ESM / TS / normalized
Runtime: node, bun 
/**
 * Derived from lodash.once@4.1.1
 * Rule-based normalized variant generated by this repository.
 * Preserve the upstream license and attribution notices when copying this file.
 */
/**
 * Derived from lodash.once@4.1.1
 * Rule-based normalized variant generated by this repository.
 * See THIRD_PARTY_NOTICES.md for upstream license and attribution details.
 */
/**
 * lodash (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */

/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = "Expected a function";

/** Used as references for various `Number` constants. */
var INFINITY = 1 / 0,
  MAX_INTEGER = 1.7976931348623157e308,
  NAN = 0 / 0;

/** `Object#toString` result references. */
var symbolTag = "[object Symbol]";

/** Used to match leading and trailing whitespace. */
var reTrim = /^\s+|\s+$/g;

/** Used to detect bad signed hexadecimal string values. */
var reIsBadHex = /^[-+]0x[0-9a-f]+$/i;

/** Used to detect binary string values. */
var reIsBinary = /^0b[01]+$/i;

/** Used to detect octal string values. */
var reIsOctal = /^0o[0-7]+$/i;

/** Built-in method references without a dependency on `root`. */
var freeParseInt = parseInt;

/** Used for built-in method references. */
var objectProto = Object.prototype;

/**
 * Used to resolve the
 * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
 * of values.
 */
var objectToString = objectProto.toString;

/**
 * Creates a function that invokes `func`, with the `this` binding and arguments
 * of the created function, while it's called less than `n` times. Subsequent
 * calls to the created function return the result of the last `func` invocation.
 *
 * @static
 * @memberOf _
 * @since 3.0.0
 * @category Function
 * @param {number} n The number of calls at which `func` is no longer invoked.
 * @param {Function} func The function to restrict.
 * @returns {Function} Returns the new restricted function.
 * @example
 *
 * jQuery(element).on('click', _.before(5, addContactToList));
 * // => Allows adding up to 4 contacts to the list.
 */
function before(n, func) {
  var result;
  if (typeof func != "function") {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  n = toInteger(n);
  return function () {
    if (--n > 0) {
      result = func.apply(this, arguments);
    }
    if (n <= 1) {
      func = undefined;
    }
    return result;
  };
}

/**
 * Creates a function that is restricted to invoking `func` once. Repeat calls
 * to the function return the value of the first invocation. The `func` is
 * invoked with the `this` binding and arguments of the created function.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Function
 * @param {Function} func The function to restrict.
 * @returns {Function} Returns the new restricted function.
 * @example
 *
 * var initialize = _.once(createApplication);
 * initialize();
 * initialize();
 * // => `createApplication` is invoked once
 */
function once(func) {
  return before(2, func);
}

/**
 * Checks if `value` is the
 * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types)
 * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an object, else `false`.
 * @example
 *
 * _.isObject({});
 * // => true
 *
 * _.isObject([1, 2, 3]);
 * // => true
 *
 * _.isObject(_.noop);
 * // => true
 *
 * _.isObject(null);
 * // => false
 */
function isObject(value) {
  var type = typeof value;
  return !!value && (type == "object" || type == "function");
}

/**
 * Checks if `value` is object-like. A value is object-like if it's not `null`
 * and has a `typeof` result of "object".
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
 * @example
 *
 * _.isObjectLike({});
 * // => true
 *
 * _.isObjectLike([1, 2, 3]);
 * // => true
 *
 * _.isObjectLike(_.noop);
 * // => false
 *
 * _.isObjectLike(null);
 * // => false
 */
function isObjectLike(value) {
  return !!value && typeof value == "object";
}

/**
 * Checks if `value` is classified as a `Symbol` primitive or object.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a symbol, else `false`.
 * @example
 *
 * _.isSymbol(Symbol.iterator);
 * // => true
 *
 * _.isSymbol('abc');
 * // => false
 */
function isSymbol(value) {
  return (
    typeof value == "symbol" || (isObjectLike(value) && objectToString.call(value) == symbolTag)
  );
}

/**
 * Converts `value` to a finite number.
 *
 * @static
 * @memberOf _
 * @since 4.12.0
 * @category Lang
 * @param {*} value The value to convert.
 * @returns {number} Returns the converted number.
 * @example
 *
 * _.toFinite(3.2);
 * // => 3.2
 *
 * _.toFinite(Number.MIN_VALUE);
 * // => 5e-324
 *
 * _.toFinite(Infinity);
 * // => 1.7976931348623157e+308
 *
 * _.toFinite('3.2');
 * // => 3.2
 */
function toFinite(value) {
  if (!value) {
    return value === 0 ? value : 0;
  }
  value = toNumber(value);
  if (value === INFINITY || value === -INFINITY) {
    var sign = value < 0 ? -1 : 1;
    return sign * MAX_INTEGER;
  }
  return value === value ? value : 0;
}

/**
 * Converts `value` to an integer.
 *
 * **Note:** This method is loosely based on
 * [`ToInteger`](http://www.ecma-international.org/ecma-262/7.0/#sec-tointeger).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to convert.
 * @returns {number} Returns the converted integer.
 * @example
 *
 * _.toInteger(3.2);
 * // => 3
 *
 * _.toInteger(Number.MIN_VALUE);
 * // => 0
 *
 * _.toInteger(Infinity);
 * // => 1.7976931348623157e+308
 *
 * _.toInteger('3.2');
 * // => 3
 */
function toInteger(value) {
  var result = toFinite(value),
    remainder = result % 1;

  return result === result ? (remainder ? result - remainder : result) : 0;
}

/**
 * Converts `value` to a number.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to process.
 * @returns {number} Returns the number.
 * @example
 *
 * _.toNumber(3.2);
 * // => 3.2
 *
 * _.toNumber(Number.MIN_VALUE);
 * // => 5e-324
 *
 * _.toNumber(Infinity);
 * // => Infinity
 *
 * _.toNumber('3.2');
 * // => 3.2
 */
function toNumber(value) {
  if (typeof value == "number") {
    return value;
  }
  if (isSymbol(value)) {
    return NAN;
  }
  if (isObject(value)) {
    var other = typeof value.valueOf == "function" ? value.valueOf() : value;
    value = isObject(other) ? other + "" : other;
  }
  if (typeof value != "string") {
    return value === 0 ? value : +value;
  }
  value = value.replace(reTrim, "");
  var isBinary = reIsBinary.test(value);
  return isBinary || reIsOctal.test(value)
    ? freeParseInt(value.slice(2), isBinary ? 2 : 8)
    : reIsBadHex.test(value)
      ? NAN
      : +value;
}

export default once;
Variant note: Rule-based normalization for modern TS projects. The goal is easier import and build compatibility, not changed behavior.
Transforms: module.exports-to-export-default, js-extension-to-ts-extension
Validation: This normalized variant is intended to stay oxlint and oxfmt clean in this repo.
Raw
CJS / JS / raw
Runtime: node, bun 
/**
 * lodash (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */

/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = 'Expected a function';

/** Used as references for various `Number` constants. */
var INFINITY = 1 / 0,
    MAX_INTEGER = 1.7976931348623157e+308,
    NAN = 0 / 0;

/** `Object#toString` result references. */
var symbolTag = '[object Symbol]';

/** Used to match leading and trailing whitespace. */
var reTrim = /^\s+|\s+$/g;

/** Used to detect bad signed hexadecimal string values. */
var reIsBadHex = /^[-+]0x[0-9a-f]+$/i;

/** Used to detect binary string values. */
var reIsBinary = /^0b[01]+$/i;

/** Used to detect octal string values. */
var reIsOctal = /^0o[0-7]+$/i;

/** Built-in method references without a dependency on `root`. */
var freeParseInt = parseInt;

/** Used for built-in method references. */
var objectProto = Object.prototype;

/**
 * Used to resolve the
 * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
 * of values.
 */
var objectToString = objectProto.toString;

/**
 * Creates a function that invokes `func`, with the `this` binding and arguments
 * of the created function, while it's called less than `n` times. Subsequent
 * calls to the created function return the result of the last `func` invocation.
 *
 * @static
 * @memberOf _
 * @since 3.0.0
 * @category Function
 * @param {number} n The number of calls at which `func` is no longer invoked.
 * @param {Function} func The function to restrict.
 * @returns {Function} Returns the new restricted function.
 * @example
 *
 * jQuery(element).on('click', _.before(5, addContactToList));
 * // => Allows adding up to 4 contacts to the list.
 */
function before(n, func) {
  var result;
  if (typeof func != 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  n = toInteger(n);
  return function() {
    if (--n > 0) {
      result = func.apply(this, arguments);
    }
    if (n <= 1) {
      func = undefined;
    }
    return result;
  };
}

/**
 * Creates a function that is restricted to invoking `func` once. Repeat calls
 * to the function return the value of the first invocation. The `func` is
 * invoked with the `this` binding and arguments of the created function.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Function
 * @param {Function} func The function to restrict.
 * @returns {Function} Returns the new restricted function.
 * @example
 *
 * var initialize = _.once(createApplication);
 * initialize();
 * initialize();
 * // => `createApplication` is invoked once
 */
function once(func) {
  return before(2, func);
}

/**
 * Checks if `value` is the
 * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types)
 * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an object, else `false`.
 * @example
 *
 * _.isObject({});
 * // => true
 *
 * _.isObject([1, 2, 3]);
 * // => true
 *
 * _.isObject(_.noop);
 * // => true
 *
 * _.isObject(null);
 * // => false
 */
function isObject(value) {
  var type = typeof value;
  return !!value && (type == 'object' || type == 'function');
}

/**
 * Checks if `value` is object-like. A value is object-like if it's not `null`
 * and has a `typeof` result of "object".
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
 * @example
 *
 * _.isObjectLike({});
 * // => true
 *
 * _.isObjectLike([1, 2, 3]);
 * // => true
 *
 * _.isObjectLike(_.noop);
 * // => false
 *
 * _.isObjectLike(null);
 * // => false
 */
function isObjectLike(value) {
  return !!value && typeof value == 'object';
}

/**
 * Checks if `value` is classified as a `Symbol` primitive or object.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a symbol, else `false`.
 * @example
 *
 * _.isSymbol(Symbol.iterator);
 * // => true
 *
 * _.isSymbol('abc');
 * // => false
 */
function isSymbol(value) {
  return typeof value == 'symbol' ||
    (isObjectLike(value) && objectToString.call(value) == symbolTag);
}

/**
 * Converts `value` to a finite number.
 *
 * @static
 * @memberOf _
 * @since 4.12.0
 * @category Lang
 * @param {*} value The value to convert.
 * @returns {number} Returns the converted number.
 * @example
 *
 * _.toFinite(3.2);
 * // => 3.2
 *
 * _.toFinite(Number.MIN_VALUE);
 * // => 5e-324
 *
 * _.toFinite(Infinity);
 * // => 1.7976931348623157e+308
 *
 * _.toFinite('3.2');
 * // => 3.2
 */
function toFinite(value) {
  if (!value) {
    return value === 0 ? value : 0;
  }
  value = toNumber(value);
  if (value === INFINITY || value === -INFINITY) {
    var sign = (value < 0 ? -1 : 1);
    return sign * MAX_INTEGER;
  }
  return value === value ? value : 0;
}

/**
 * Converts `value` to an integer.
 *
 * **Note:** This method is loosely based on
 * [`ToInteger`](http://www.ecma-international.org/ecma-262/7.0/#sec-tointeger).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to convert.
 * @returns {number} Returns the converted integer.
 * @example
 *
 * _.toInteger(3.2);
 * // => 3
 *
 * _.toInteger(Number.MIN_VALUE);
 * // => 0
 *
 * _.toInteger(Infinity);
 * // => 1.7976931348623157e+308
 *
 * _.toInteger('3.2');
 * // => 3
 */
function toInteger(value) {
  var result = toFinite(value),
      remainder = result % 1;

  return result === result ? (remainder ? result - remainder : result) : 0;
}

/**
 * Converts `value` to a number.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to process.
 * @returns {number} Returns the number.
 * @example
 *
 * _.toNumber(3.2);
 * // => 3.2
 *
 * _.toNumber(Number.MIN_VALUE);
 * // => 5e-324
 *
 * _.toNumber(Infinity);
 * // => Infinity
 *
 * _.toNumber('3.2');
 * // => 3.2
 */
function toNumber(value) {
  if (typeof value == 'number') {
    return value;
  }
  if (isSymbol(value)) {
    return NAN;
  }
  if (isObject(value)) {
    var other = typeof value.valueOf == 'function' ? value.valueOf() : value;
    value = isObject(other) ? (other + '') : other;
  }
  if (typeof value != 'string') {
    return value === 0 ? value : +value;
  }
  value = value.replace(reTrim, '');
  var isBinary = reIsBinary.test(value);
  return (isBinary || reIsOctal.test(value))
    ? freeParseInt(value.slice(2), isBinary ? 2 : 8)
    : (reIsBadHex.test(value) ? NAN : +value);
}

module.exports = once;
Variant note: Published package file kept as-is for older teams or repos that still prefer the original CommonJS distribution.