for...of 语句执行一个循环,该循环处理来自可迭代对象的值序列。可迭代对象包括内置对象的实例,例如 Array、String、TypedArray、Map、Set、NodeList(以及其他 DOM 集合),还包括 arguments 对象、由生成器函数生成的生成器,以及用户定义的可迭代对象。
for (let i = "start" in window ? window.start : 0; i < 9; i++) { console.log(i); } // SyntaxError: 'for-in' loop variable declaration may not have an initializer. jsCopy to Clipboard // 将整个初始化器括起来 for (let i = ("start" in window ? window.start : 0); i <...
1let iterable = [10, 20, 30];23for(let value of iterable) {4value += 1;5console.log(value);6} The code 's output: 11 21 31 Related Pages: JavaScriptfor :http://www.runoob.com/js/js-loop-for.html JavaScriptfor/in :http://www.runoob.com/jsref/jsref-forin.html MDN - for....
In JavaScript, theforloop can be achieved in different ways -for,for...in,for...of, andforEach- which are useful for different case scenarios.for..ofallows us to access the element of the array directly without having to use any index value which is typically inserted into the array squ...
这种非标准的方式已经在40的版本之后被移除了. 现在开始它会在控制台里抛出一个SyntaxError("for-in loop head declarations may not have initializers") 警告。(bug 748550以及bug 1164741)。 像其他引擎 V8(Chrome),Chakra (IE/Edge), JSC (WebKit/Safari) 正在研究去除这种不标准的行为。
简单说，for in是遍历键名，for of是遍历键值。例如：let arr = ["a","b"];for (a in arr) { console.log(a);//1,2}for (a of arr) { console.log(a);//a,b}由于for of的这个特性，他还可以实现对iterator对象的遍历，而for in就是简单的遍历了。
Async iterators are a feature in modern JavaScript that allow you to consume data asynchronously. They're useful for handling paginated data from APIs. Async iterators use thefor-await-ofloop to iterate over data, fetching it as needed.
平时工作中循环的使用场景可以说是非常之多了,昨天改别人代码时候有位同事非常喜欢用ES6等新特性,一个数组的遍历全部都是用for...of...,然后业务需求要用...
According to MDN, the for...in loop should not be used to iterate over an array where the index order is important. This loop does not guarantee to return the indexes in the original order. Instead, you should use a simple for loop with a numeric index or for...of loop when ite...
In chrome://flags/#enable-javascript-harmony, activate the entry “Enable Experimental JavaScript”. [2] Prior Firefox 51, using the for...of loop construct with the const keyword threw a SyntaxError ("missing = in const declaration"). This has been fixed (bug 1101653). [3] Support for ...