教你如何一步步迷上JS.. ╮(╯▽╰)╭

Teach you how to fall in love with JS step by step.. ╮(╯▽╰)╭

好嘀,只是一些总结

JS中的那些萌点

  • <script>标签中，合理使用defer="defer"(延迟执行)，async="async"(异步执行)
  • 外部JS可以使用其它扩展名(如.php)，但必须返回正确MINE类型
  • 使用var obj = preferredObj || backupObj; 提供后备值 ::aru:surprised::
  • 函数中使用arguements[]获取参数
  • 无函数签名，再见吧重载 ::aru:meditation::
  • 函数无引用传参，只要不作死用全局变量，封装就很完美
  • 神奇的垃圾收集功能，开发时无需考虑手动释放内存
  • 函数传参使用function hh({})直接传包含参数的对象，更加灵活
  • 数组每一个位置可以存不同类型的数据 ::aru:blood2::
  • 数组支持模拟栈操作，如push()和pop()
  • 数组支持模拟队列操作，如push()和shift()
  • 数组支持从相反方向模拟队列，如unshift()和pop()
  • sort()可自定义比较函数为参数
  • 数组splice()可太好用了吧
  • 函数是对象，函数名是指针
  • 可以像传递参数一样把一个函数传给另一个函数，也可以将一个函数作为另一个函数的结果返回
  • 函数中可通过arguments.callee获取当前函数名指针
  • 使用arguments.callee.caller获取调用当前函数的引用
  • 使用function.apply(this/*作用域*/, arguments)或function.call(this, arg1, arg2...)指定作用域运行函数
  • 使用函数固有属性function.length获取其期待的参数个数
  • 通过函数继承属性toLocaleString()``toString()``valueOf()返回代码，方便调试
  • 使用indexOf()``lastIndexOf()查找元素出现位置
  • trim()删除字符串开头结尾空格
  • 支持正则RegExp
  • 神奇但可怕的eval("")可将字符串转译成代码并就地执行
  • encodeURI()/decodeURI()与encodeURIComponent()/decodeURICompoent()处理uri
  • 立即调用函数function(){}();
  • 内置Math对象
  • Math中ceil()``floor()``round()向上，向下，标准舍入
  • Math.random()大于零小于一随机数
  • 对象中使用functionName: function(){}直接定义函数
  • ES6中(x)=>x+1等价于function(x){return x+1;}
  • 使用;(function(name, context, definition){moudle.exports = definition();})('funationName', this, function(){});封装模块

小心得

  • 不建议使用with语句
  • label标签少用
  • 0.1 + 0.2 != 0.3 浮点型天坑，与C类似
  • ~26 == -27 利用按位非提高效率
  • 标识符查询由内部环境向外部环境进行
  • 没有块级作用域，与C++不同
  • var obj2 = obj1;实际是引用
  • 函数传参时传对象，实际传的是指针
  • 全局变量用完及时置为null以提性能
  • 使用变量属性访问对象只能使用obj[var]
  • var sum = function sum(){};在Safari中会报错
  • 不能为基本类型值添加属性和方法
  • new Number("25")返回对象，而Number("25")返回25
  • 布尔表达式中对象均为true

Okay, just some summary

Those cute points in JS

  • In the <script> tag, reasonably use defer="defer" (delayed execution) and async="async" (asynchronous execution)
  • External JS can use other extensions (such as .php), but must return the correct MINE type
  • Use var obj = preferredObj || backupObj; to provide a backup value ::aru:surprised::
  • Use arguements[] to get parameters in the function
  • No function signature, goodbye overload ::aru:meditation::
  • The function has no reference to pass parameters, as long as the global variable is not used for deadly, the encapsulation is perfect
  • Magic garbage collection function, no need to consider manually releasing memory during development
  • Use function hh({}) to pass parameters directly to functions, which is more flexible
  • Each position of the array can store different types of data ::aru:blood2::
  • Array supports simulated stack operations, such as push() and pop()
  • Array supports simulated queue operations, such as push() and shift()
  • Array supports simulating queues from the opposite direction, such as unshift() and pop()
  • sort() can customize the comparison function as a parameter
  • The array splice() is so easy to use, right?
  • Functions are objects and function names are pointers
  • You can pass a function to another function as parameters, or you can return a function as the result of another function
  • In the function, the current function name pointer can be obtained through arguments.callee
  • Use arguments.callee.caller to get a reference to call the current function
  • Use function.apply(this/*scope*/, arguments) or function.call(this, arg1, arg2...) to specify the scope to run the function
  • Use the function intrinsic property function.length to get the number of expected parameters
  • Inherit the property toLocaleString(), toString(), and valueOf() return code through the function to facilitate debugging
  • Use indexOf() and lastIndexOf() to find the element’s appearance
  • trim() delete spaces at the beginning and end of the string
  • Support regular RegExp
  • The magical but terrible eval("") can translate the string into code and execute it in place
  • encodeURI()/decodeURI() and encodeURIComponent()/decodeURICompoent() handle uri
  • Call the function immediately function()()();
  • Built-in Math object
  • ceil(), floor(), round() in Math up, down, standard rounding
  • Math.random() is a random number greater than zero and less than one
  • Use functionName: function(){} in the object to directly define the function
  • In ES6 (x)=>x+1 is equivalent to function(x){return x+1;}
  • Use ;(function(name, context, definition){moudle.exports = definition();})('funationName', this, function()()); to encapsulate the module

Be careful

  • It is not recommended to use with statement
  • Less use of label
  • 0.1 + 0.2 != 0.3 floating point tiankeng, similar to C
  • ~26 == -27 Use bitwise not to improve efficiency
  • Identifier query is carried out from the internal environment to the external environment
  • No block-level scope, different from C++
  • var obj2 = obj1; is actually a reference
  • The object is passed when the function is passed, but the pointer is actually passed
  • Set global variables to null when used up to improve performance
  • Use variable attributes to access objects can only use obj[var]
  • var sum = function sum(){}; will report an error in Safari
  • You cannot add attributes and methods to basic type values
  • new Number("25") returns the object, and Number("25") returns 25
  • All objects in Boolean expressions are true