[英]Does JavaScript have an indexOf(lambda) or similar?
I want to return the index of the first element satisfying a unary predicate. 我想返回满足一元谓词的第一个元素的索引。
Example: 例:
[1,2,3,4,5,6,7].indexOf((x) => x % 3 === 0) // returns 2
Is there such a function? 有这样的功能吗? The alternative I was going to use was
我打算用的替代方案是
[1,2,3,4,5,6,7].reduce((retval,curelem,idx) =>
{
if(curelem % 3 === 0 && retval === undefined)
retval = idx;
return retval;
}, undefined);
but of course that would be less efficient since it doesn't stop iterating through the array after it has found the element. 但是当然效率会降低,因为它在找到元素后不会停止遍历数组。
Yes, there is such function: Array.prototype.findIndex
. 是的,有这样的功能:
Array.prototype.findIndex
。 The method was introduced by ECMAScript 2015 and you need to use a polyfill for supporting older browsers. 该方法由ECMAScript 2015引入,您需要使用polyfill来支持旧版浏览器。
是的它存在:
console.log([1,2,3,4,5,6,7].findIndex((x) => x % 3 === 0));
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