后盾人JS--JS值类型使用
章节介绍与类型判断
看看构造函数
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>let hd=[]let hdcms = {}console.log(hd instanceof Array) //判断是否在原型链上（是否由这个构造函数创建出来console.log(hdcms instanceof Object)</script>
</body>
</html>都是true
字符串转义与模板字面量使用
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>let hd = 'houdun\'人'console.log(hd)</script>
</body>
</html>加个\就成了
模板字面量浅谈使用技巧
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>let lessons= [{title:"媒体查询响应式布局"},{title:"FLEX弹性盒模型"},{title:"GRID栅格系统"}]function template(){return `<ul>${lessons.map(item=>`<li>${item.title}</li>`).join('')}</ul>`}document.body.innerHTML=template()
</script>
</body>
</html>神奇的标签模板实例操作
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>let name = '后盾人'let web = "houdunren.com"console.log(tag`在线教程${name}，网址是${web}`)function tag(strings,...vars){console.log(vars)console.log(strings)}</script>
</body>
</html>
打印出来是这样的
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head><body><script>let lessons = [{ title: "后盾人媒体查询响应式布局", author: '后盾人向军' },{ title: "FLEX弹性盒模型", author: '后盾人' },{ title: "GRID栅格系统后盾人教程", author: '古老师' }]function template() {return `<ul>${lessons.map(item => links`<li>作者：${item.author},课程：${item.title}</li>`).join('')}</ul>`}function links(strings, ...vars) {return strings.map((str, key) => { //将字符替换成链接return str + (vars[key] ? vars[key].replace("后盾人",`<a href="https://www.houdunren.com"> 后盾人</a>`) : "") //变量数量多}).join('')}document.body.innerHTML += template()</script>
</body></html>这是把字符替换成链接了
字符串及基本函数使用
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><input type="text" name="password"><span></span><script>let ps = document.querySelector("[name='password']")ps.addEventListener('keyup',function(){this.value = this.value.trim()let error = " "let span = document.getElementsByTagName('span')if(this.value.length<5){error="密码不能小于五位"}span[0].innerHTML=error})</script>
</body>
</html>可以做渐变（可能）效果
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>let hd = 'houdunren'for(let i =0;i<hd.length;i++){let span = document.createElement("span")span.style.fontSize = (i+1)*10+'px'span.innerHTML = hd[i]document.body.append(span)}</script>
</body>
</html>字符串截取操作
让我们看一下字符串的截取操作
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>let hd = "houdunren.com"console.log(hd.slice(1,3))console.log(hd.substr(1,3))console.log(hd.substring(1,3))console.log(hd.slice(-3,-1))console.log(hd.substr(-3))console.log(hd.substring(-3,2))</script>
</body>
</html>
解锁字符串使用技巧
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head><body><script>const hd = "houdunren.com"//从哪个位置开始找，找不到就是-1if (hd.indexOf('h') != -1) {console.log('找到了')}console.log(hd.includes("h",8)) //和上面的作用一样console.log(hd.startsWith('H')) //返回布尔类型，看是否在开始console.log(hd.lastIndexOf('o',9)) //从后向前查</script>
</body></html>这是数组的some方法
查找字符串方法：
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>const word = ["php","css"]const string = "我喜欢在后盾人学习php与css芝士"const status = word.some(word=>{console.log(word)return string.includes(word)})if(status){console.log('找到了')}</script>
</body>
</html>字符串替换标题关键词
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>const hd = "houdunren.com"console.log(hd.replace('houdunren','hdcms'))const word = ["php" , "css"]const string = "我其实不喜欢学php和css"const repaceString = word.reduce((pre,word)=>{return pre.replace(word,`<a href="?w=${word}">${word}</a>`)},string)console.log(repaceString)document.body.innerHTML += repaceString</script>
</body>
</html>
好吧，好难理解 