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In JavaScript, three dots "..." represent the spread operator, which is a new addition in ES6. It can add array expressions or strings in the syntax during function call/array construction. Level expansion; you can also expand object expressions in a "key-value" manner when constructing literal objects.
The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.
When we look at js code, three dots (...) often appear. What does it mean? What's the use?
Now I will share with you the things about the three points
The real name of the three dots (...) is the expansion operator, which is a new addition in ES6. It can expand array expressions or strings at the syntax level during function calls/array construction; You can also expand the object expression in a key-value manner when constructing a literal object
Literals generally refer to the simplicity of [1,2,3] or {name:'chuichui'} The construction method, multi-layer nested arrays and objects are powerless with three points
To put it bluntly, it means taking off the clothes, whether it is braces ([]) or curly braces ({}) , it’s no big deal, take them all off, take them off!
// 数组 var number = [1,2,3,4,5,6] console.log(...number) //1 2 3 4 5 6 //对象 var man = {name:'chuichui',height:176} console.log({...man}) / {name:'chuichui',height:176}
It has a wide range of uses, we can see it everywhere, here are a few common examples
//数组的复制 var arr1 = ['hello'] var arr2 =[...arr1] arr2 // ['hello'] //对象的复制 var obj1 = {name:'chuichui'} var obj2 ={...arr} ob12 // {name:'chuichui'}
//数组的合并 var arr1 = ['hello'] var arr2 =['chuichui'] var mergeArr = [...arr1,...arr2] mergeArr // ['hello','chuichui'] // 对象分合并 var obj1 = {name:'chuichui'} var obj2 = {height:176} var mergeObj = {...obj1,...obj2} mergeObj // {name: "chuichui", height: 176}
var arr1 = [...'hello'] arr1 // ["h", "e", "l", "l", "o"]
Can be combined with normal functions and used flexibly
function f(v,w,x,y,z){ } var args = [2,3] f(1,...args,4,...[5])
When we want to add elements in an array Use it when iterating as function parameters!
function f(x,y,z){} var args = [1,2,3] f(...args) // 以前的方法 f.apply(null,args);
[Recommended learning: javascript advanced tutorial]
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