What do multiple dots mean in JavaScript?

In JavaScript, multiple dots "..." refer to the spread operator, which is a newly added feature in ES6. It can convert array expressions or String is expanded at the syntax level; object expressions can also be expanded in a "key-value" manner when constructing literal objects.

The operating environment of this tutorial: Windows 7 system, ECMAScript version 6, Dell G3 computer.

In JavaScript, the three dots (...) are really called the spread operator, which is a new addition in ES6. It can add an array expression or string to the function call/array construction. Expansion at the syntax level; you can also expand the object expression in a key-value manner when constructing a literal object

Literals generally refer to [1,2,3] or {name:'chuichui' }With this simple construction method, the three points of multi-layered nested arrays and objects are powerless.

To put it bluntly, it means taking off the clothes, whether it is braces ([]), curly braces ({}), don’t worry about it,take them all 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}

What’s the use?

Its use is very wide, we can see it everywhere, here are a few common examples

Copy and use it

//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'}

Merge and use it

//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}

Use it to convert characters to arrays

var arr1 = [...'hello'] arr1 // ["h", "e", "l", "l", "o"]

Use it to pass function parameters

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 use arrays Use it when the elements in iterate 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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