JS学习笔记——基础语法

js

变量

  1. 浮点数可用科学记数法
  2. 创建数组
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    var chars = new Array();
    var chars = new Array("a","b","c");
    var chars = ["a","b","c"];
  3. 字符串与数字相加
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    var num = 5 + "5";
    输出为num值为55
  4. ===表示全等，即类型与值都相等

控制语句

  1. label可用于标记语句 
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    people = ["wang","zhang","li"];
    loop:
    for(var i=0;i<people.length;++i){
      for(var j=0;j<people[i].length;++j)
        if(people[i][j] == "h")
          break loop;
        else
          alert(people[i][j]);
      alert(i);
    }
  2. throw语句创建自定义错误。 
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    try {
        if(obj == null ) throw "Object is empty";
        if(obj == undefined ) throw "Object is undefined";
    } catch (err){
        var msg = document.getElementById("msg");
        msg.innerHtml = "Error : " + err.message + ".";
    }
  3. 不推荐使用with，容易产生歧义以及潜在的bug