前端面试题总结（持续更新）_html/css_WEB-ITnose
接下来要参与大大小小的暑期实习笔试和面试。在这篇博客里我将总结一些常见的面试题。其中有一部分是我去年暑假找实习的时候总结的。现在看来，不免有些幼稚。慢慢完善吧！
JavaScript
Q：JS中的闭包
A：闭包从本身在函数式编程中的概念来说，说的是在定义函数时的两部分-函数体和函数的 context，也就是函数定义时的上下文。里面保存着作用域中的变量，函数的定义和赋值。
而我们平时说的闭包，其实是创建对于这个上下文的引用，从而在外部作用域中通过这个引用来访问这个上下文。
所以从概念上来说，你声明了一个函数，就声明了一个闭包。
然后从实际的使用来说，当你通过某种代码对在外部作用域中保存了对当前闭包的引用时，我们说你就“创建”了一个闭包，其实是“创建”了一个 闭包的引用。我们通常用IIFE来达到这一效果，以至于有人认为IIFE就是“闭包”，这其实是不正确的认识。
这就是闭包的实质，至于如何去使用闭包，那就五花八门了。你可以用来保存被外部作用域访问的临时变量，也可以用来封装函数，也可以用来做访问权限控制（类似Java中的私有变量）。
Q：JS模块化
A：
- 为什么我们需要JS模块化
- JS模块化的发展过程（从function，IIFE到Commonjs）
- JS模块化的几种方案介绍（Commonjs，AMD，ES6 Module）
CSS
Q：CSS position的不同取值以及差异？
A：取值：static（默认），relative，absolute，fixed。差异，relative：相对于其自身进行定位，不脱离文档流。absolute：相对于父元素链上的第一个已定位元素，如果不存在则相对于body。脱离文档流。fixed，相对于浏览器窗口进行定位，脱离文档流。static：正常的文档流定位。
Q：CSS 盒模型
A：
- W3C 默认 content-box，ie5-、ie6 Quirks mode border-box
- content-box：csswidth = content width
- border-box: csswidth = content width + padding +border
Q：CSS选择器
A：元素，类，id，属性，伪类，伪元素。···
Q：CSS hack
A：选择器hack（-webkit-,-moz-）,属性hack，IE条件注释
HTML
Q：web语义化
A：
html5新标签：
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