使用驼峰名法:首字母小写,其他的有意义的单词大写(尽可能语义化) add/insert/create/new (新增) rm (删除) sel/select/query/get (查询) info (信息) 1. 2. 3. 4. 不能使用关键字和保留字 JS中常用的数据类型 基本数据类型 数字nubmer (常规数字/NaN) 字符串 string (所有单引号、
DOCTYPE html>JavaScript debugging example//create a global variable for our vardisplay;functioninit() {//initialize only after the HTML has been loadeddisplay=document.getElementById("results"); }functionfirstParam() {//set breakpoint herevara=5; secondParam(a); }functionsecondParam(a) {varb=...
ES6 又新增了块级作用域,本教程不涉及。 函数外部声明的变量就是全局变量(global variable),它可以在函数内部读取。 varv =1;functionf() {console.log(v); } f()// 1 上面的代码表明,函数f内部可以读取全局变量v。 在函数内部定义的变量,外部无法读取,称为“...
The scope containing all of a program is calledglobal scopeorprogram scope.This is the scope you are in when entering a script (be it atag in a web page or be it a.jsfile). Inside the global scope, you can create a nested scope by defining a function. Inside such a function, you...
JavaScript是一种解释执行的脚本语言,是一种动态类型、弱类型、基于原型的语言,内置支持类型,它遵循ECMAScript标准。它的解释器被称为JavaScript引擎,为浏览器的一部分,广泛用于客户端的脚本语言,主要用来给HTML增加动态功能。
varname ="Jack";// local variable; only accessible in this showName function console.log (name);// Jack } console.log (name); // Richard: the global variable 没有块级作用域: varname ="Richard"; // the blocks in this if statement do not create a local context for the name variable...
Now, for convenience, let’s create a reference to thewhoAmImethod, presumably so we can access it merely bywhoAmI()rather than the longerobj.whoAmI(): varwhoAmI = obj.whoAmI; And just to be sure we’ve stored a reference to a function, let’s print out the value of our newwhoAmIva...
Global variables defined with theletkeyword do not belong to the window object: Example letcarName ="Volvo"; // code here can not use window.carName Try it Yourself » Warning Do NOT create global variables unless you intend to. Your global variables (or functions) can overwrite window vari...
varx="global";functionf(){varx="local"; console.log(x);// local}f();console.log(x);// global复制代码 这就是覆盖的作用域。 三. JavaScript 中变量的作用域 大多数的主流语言都是有块级作用域的,变量在最近的代码块中,Objective-C和Swift都是块级作用域的。但是在 JavaScript 中的变量是函数级...
Toassigna value to the variable, use the equal sign: carName ="Volvo"; You can also assign a value to the variable when you declare it: letcarName ="Volvo"; In the example below, we create a variable calledcarNameand assign the value "Volvo" to it. ...