小蘑菇的技术之路
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JavaScript 语法

发表于 更新于 分类于

var let const

let 不能声明多次

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var i = "global";

function test () {
  var i = "function";
  console.log(i);
}

test();
console.log(i);

/*
console log:
"function"
"global"
*/
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var i = "global";

function test () {
  i = "function";
  console.log(i);
}

test();
console.log(i);

/*
console log:
"function"
"function"
*/
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function test () {
  i = "function";
  console.log(i);
}

test();
console.log(i);

/*
console log:
"function"
"function"
*/
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let i = "global";
function test () {
  let i = "function";
  console.log(i);
}

test();
console.log(i);

/*
console log:
"function"
"global"
*/
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let i = "global";
function test () {
  i = "function";
  console.log(i);
}

test();
console.log(i);

/*
console log:
"function"
"function"
*/
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function test () {
  let i = "function";
  console.log(i);
}

test();
console.log(i);

/*
console log:
Uncaught ReferenceError: i is not defined 
*/

Object.freeze()

undefined null

===

!==

Array

push pop

shift unshift

Math.random()

Math.floor()

parseInt()

字符串 -> 数值

Arrow Function

匿名函数

Rest Operator

参数封装为数组

Spread Operator

深拷贝

use strict

import requires

import * as … from …

export default

默认导出，引用时无需使用 {}

import subtract from …