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cond.ts
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cond.ts
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import map from './map.js';
/**
* Creates a function that iterates over `pairs` and invokes the corresponding
* function of the first predicate to return truthy. The predicate-function
* pairs are invoked with the `this` binding and arguments of the created
* function.
*
* @since 4.0.0
* @category Util
* @param {Array} pairs The predicate-function pairs.
* @returns {Function} Returns the new composite function.
* @example
*
* const func = cond([
* [matches({ 'a': 1 }), () => 'matches A'],
* [conforms({ 'b': isNumber }), () => 'matches B'],
* [() => true, () => 'no match']
* ])
*
* func({ 'a': 1, 'b': 2 })
* // => 'matches A'
*
* func({ 'a': 0, 'b': 1 })
* // => 'matches B'
*
* func({ 'a': '1', 'b': '2' })
* // => 'no match'
*/
function cond(pairs: any[]) {
const length = pairs == null ? 0 : pairs.length;
pairs = !length
? []
: map(pairs, (pair: any[]) => {
if (typeof pair[1] !== 'function') {
throw new TypeError('Expected a function');
}
return [pair[0], pair[1]];
});
// eslint-disable-next-line consistent-return
return function (this: any, ...args: any[]) {
for (const pair of pairs) {
if (pair[0].apply(this, args)) {
return pair[1].apply(this, args);
}
}
};
}
export default cond;