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前言
1let篇
1.1作用域
1.2变量提升
1.3相同作用域赋值
2const篇
3模板字符串篇
3.1传统
3.2模板字符串复制
4扩展运算符篇
4.1传统赋值
4.2扩展字符串复制 前言
ES6是前端面试中常考查得知识点#xff0c;还请大家不断得去琢磨琢磨
let篇
!DOCTYPE h…目录
前言
1let篇
1.1作用域
1.2变量提升
1.3相同作用域赋值
2const篇
3模板字符串篇
3.1传统
3.2模板字符串复制
4扩展运算符篇
4.1传统赋值
4.2扩展字符串复制 前言
ES6是前端面试中常考查得知识点还请大家不断得去琢磨琢磨
let篇
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptfor (var i 0; i 6; i) {}console.log(i);/script/body/html !DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptfor (let i 0; i 6; i) {}console.log(i);/script/body/html 作用域不同
var声明的是全局变量在函数内未使用var声明的变量自动变为全局变量 let 声明一个块级作用域的变量有暂时性死区 所谓暂时性死区就是在声明变量前使用变量就会报错
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptconsole.log(i);var i;/script/body/html !DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptconsole.log(i);let i;/script/body/html 变量提升现象
var声明的变量会被提升到作用域顶部并初始化为undefined,let声明的变量不会被提升到顶部也未被初始化
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptvar i 100;var i 200;console.log(i);/script/body/html !DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptlet i 100;let i 200;console.log(i);/script/body/html 相同作用域重复命名变量
var 声明的变量是允许重复命名的且后边的会覆盖掉前边的变量
let 声明的变量是不允许重复命名相同变量的let,会报错
const篇
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptconst i 200;console.log(i);i 200;/script/body/html const声明一个只读的常量一旦声明就不能改变也就意味着声明的时候就必须赋值 不能像var那样留在以后赋值否则就会报错其他和let相同
模板字符串篇
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptlet name geyaolet age 19str 名字 name 年龄 age;console.log(str);/script/body/html !DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptlet name geyaolet age 19let str1 我的名字叫${name}我今年${age}岁;console.log(str1);/script/body/html 扩展运算符篇
传统复制
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptlet arr [geyao]let arr1 [woshi]arr1 arr.concat(arr1);console.log(arr1);/script/body/html 扩展运算符
!DOCTYPE html
html langenheadmeta charsetUTF-8meta nameviewport contentwidthdevice-width, initial-scale1.0titleDocument/title
/headbodyscriptlet arr [geyao]arr.push(...[1, 2, 3])console.log(arr);/script/body/html 结尾
先说说常见得这几种吧后续有什么新得理解和体会在做补充
最近没啥灵感等想到我在说故事。后面还有钩子函数module有时间再做说明
