45 lines
1.5 KiB
JavaScript
45 lines
1.5 KiB
JavaScript
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//#region src/compat/function/bind.ts
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/**
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* Creates a function that invokes `func` with the `this` binding of `thisArg` and `partials` prepended to the arguments it receives.
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*
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* The `bind.placeholder` value, which defaults to a `symbol`, may be used as a placeholder for partially applied arguments.
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*
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* Note: Unlike native `Function#bind`, this method doesn't set the `length` property of bound functions.
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*
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* @param {(...args: any[]) => any} func - The function to bind.
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* @param {any} thisObj - The `this` binding of `func`.
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* @param {...any} partialArgs - The arguments to be partially applied.
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* @returns {(...args: any[]) => any} - Returns the new bound function.
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*
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* @example
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* function greet(greeting, punctuation) {
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* return greeting + ' ' + this.user + punctuation;
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* }
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* const object = { user: 'fred' };
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* let bound = bind(greet, object, 'hi');
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* bound('!');
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* // => 'hi fred!'
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*
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* bound = bind(greet, object, bind.placeholder, '!');
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* bound('hi');
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* // => 'hi fred!'
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*/
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function bind(func, thisObj, ...partialArgs) {
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const bound = function(...providedArgs) {
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const args = [];
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let startIndex = 0;
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for (let i = 0; i < partialArgs.length; i++) {
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const arg = partialArgs[i];
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if (arg === bind.placeholder) args.push(providedArgs[startIndex++]);
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else args.push(arg);
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}
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for (let i = startIndex; i < providedArgs.length; i++) args.push(providedArgs[i]);
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if (this instanceof bound) return new func(...args);
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return func.apply(thisObj, args);
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};
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return bound;
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}
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bind.placeholder = Symbol("bind.placeholder");
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//#endregion
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export { bind };
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