循环一遍又一遍地触发,没有什么异步的,这就是引擎盖下发生的事情:reduce() while() callback() while (k < len) { if (k in o) { value = callback(value, o[k], k, o); } k++; } 真正的魔力就发生在这儿: return previousPromise.then(() => { return methodThatReturnsAPromise(nextID) ...
MDN example 往往地 reduce语法 (method) Array<number>.reduce(callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number (+2 overloads) Calls the specified callback function for all the elements in an array. The re...
文章目录 reduce语法reducerreduce() reduce()的运行过程reduce()的运行过程reducerresult 综合测试代码MDN example 往往地 reduce语法 (method) Array<number>.reduce(callbackfn: (p
reduce() 方法对数组中的每个元素按序执行一个提供的 reducer 函数,每一次运行 reducer 会将先前元素的计算结果作为参数传入,最后将其结果汇总为单个返回值。
A more real-world example is to remove duplicates from an array. Here we can be slightly clever. First,filter()actually returns a callback function for each element in an array that is invoked with three arguments: element, index, and array. Second, the built-in array methodindexOfreturns...
开篇语: 一直以来都知道数组有一个reduce方法,可是在工作过程中很少用到,对其用法也不是很清晰,今天抽时间好好整理一下,希望加深记忆,以后在工作过程中做到手到擒来,得心应手。1、概念首先看一下reduce函数在mdn上的概念:Thereduce() method executes areduce ...
Thereducemethod executes thecallbackfunction once for each element present in the typed array, excluding holes in the typed array, receiving four arguments: the initial value (or value from the previouscallbackcall), the value of the current element, the current index, and the typed array over...
With all that in mind, the real magic occurs in this piece right here: returnpreviousPromise.then(()=>{returnmethodThatReturnsAPromise(nextID)}); Each time our callback fires, we return a promise that resolves toanotherpromise. And whilereduce()doesn’t wait for any resolution to take pla...
javascript Array扩展 2009-09-20 23:51 −最近看了一下developer.mozilla.org里的东西,发现它为Array对象添加了不少generic method,赶得上Prototype的热心程度。 indexOf 返回元素在数组的索引,没有则返回-1。与string的indexOf方法差不多。 如果其他浏览器没有实现此方法,可以用以下... ...
Reduce，就像map和filter一样，遍历数组中的每个元素。它有一个累加器和一个当前值，你应该总是返回累加...