48 lines
1.7 KiB
JavaScript
48 lines
1.7 KiB
JavaScript
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import _concat from "./internal/_concat.js";
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import _curry1 from "./internal/_curry1.js";
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import curryN from "./curryN.js";
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/**
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* Creates a new list iteration function from an existing one by adding two new
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* parameters to its callback function: the current index, and the entire list.
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*
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* This would turn, for instance, [`R.map`](#map) function into one that
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* more closely resembles `Array.prototype.map`. Note that this will only work
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* for functions in which the iteration callback function is the first
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* parameter, and where the list is the last parameter. (This latter might be
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* unimportant if the list parameter is not used.)
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*
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* @func
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* @memberOf R
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* @since v0.15.0
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* @category Function
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* @category List
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* @sig (((a ...) -> b) ... -> [a] -> *) -> (((a ..., Int, [a]) -> b) ... -> [a] -> *)
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* @param {Function} fn A list iteration function that does not pass index or list to its callback
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* @return {Function} An altered list iteration function that passes (item, index, list) to its callback
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* @example
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*
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* const mapIndexed = R.addIndex(R.map);
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* mapIndexed((val, idx) => idx + '-' + val, ['f', 'o', 'o', 'b', 'a', 'r']);
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* //=> ['0-f', '1-o', '2-o', '3-b', '4-a', '5-r']
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*/
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var addIndex =
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/*#__PURE__*/
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_curry1(function addIndex(fn) {
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return curryN(fn.length, function () {
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var idx = 0;
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var origFn = arguments[0];
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var list = arguments[arguments.length - 1];
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var args = Array.prototype.slice.call(arguments, 0);
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args[0] = function () {
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var result = origFn.apply(this, _concat(arguments, [idx, list]));
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idx += 1;
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return result;
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};
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return fn.apply(this, args);
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});
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});
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export default addIndex;
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