30 lines
1.1 KiB
JavaScript
30 lines
1.1 KiB
JavaScript
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// Some functions take a variable number of arguments, or a few expected
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// arguments at the beginning and then a variable number of values to operate
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// on. This helper accumulates all remaining arguments past the function’s
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// argument length (or an explicit `startIndex`), into an array that becomes
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// the last argument. Similar to ES6’s "rest parameter".
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function restArguments(func, startIndex) {
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startIndex = startIndex == null ? func.length - 1 : +startIndex;
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return function() {
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var length = Math.max(arguments.length - startIndex, 0),
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rest = Array(length),
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index = 0;
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for (; index < length; index++) {
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rest[index] = arguments[index + startIndex];
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}
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switch (startIndex) {
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case 0: return func.call(this, rest);
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case 1: return func.call(this, arguments[0], rest);
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case 2: return func.call(this, arguments[0], arguments[1], rest);
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}
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var args = Array(startIndex + 1);
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for (index = 0; index < startIndex; index++) {
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args[index] = arguments[index];
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}
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args[startIndex] = rest;
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return func.apply(this, args);
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};
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}
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module.exports = restArguments;
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