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40 lines
1.0 KiB
TypeScript
40 lines
1.0 KiB
TypeScript
// Loaded from https://deno.land/x/ramda@v0.27.2/source/once.js
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import _arity from './internal/_arity.js';
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import _curry1 from './internal/_curry1.js';
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/**
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* Accepts a function `fn` and returns a function that guards invocation of
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* `fn` such that `fn` can only ever be called once, no matter how many times
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* the returned function is invoked. The first value calculated is returned in
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* subsequent invocations.
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*
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* @func
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* @memberOf R
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* @since v0.1.0
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* @category Function
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* @sig (a... -> b) -> (a... -> b)
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* @param {Function} fn The function to wrap in a call-only-once wrapper.
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* @return {Function} The wrapped function.
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* @example
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*
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* const addOneOnce = R.once(x => x + 1);
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* addOneOnce(10); //=> 11
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* addOneOnce(addOneOnce(50)); //=> 11
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*/
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var once = _curry1(function once(fn) {
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var called = false;
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var result;
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return _arity(fn.length, function() {
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if (called) {
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return result;
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}
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called = true;
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result = fn.apply(this, arguments);
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return result;
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});
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});
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export default once;
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