JavaScript02-常见语法

1.基本语法(常量，属性定义)

    <script text="text/javascript">
        //1.基本语法
        var age = 18;                   //number
        var money = 10.88;              //number
        var name = 'Steven';            //string
        var family_name = "Rose";       //string
        var result = true;//false       //boolean
        var number = null;//为空         //object
        var number2 = undefined;//未定义 //undefined
    </script>

2.如何进行输出(类型)

    <script text="text/javascript">
        //2.如何进行输出
  console.log(age,money,name,family_name,result,number,number2);

        //3.变量的真实类型 typeof
        console.log(typeof age,typeof money,typeof name,typeof family_name,typeof result,typeof number,typeof number2);
        //number number string string boolean object undefined
    </script>

3.基本数据类型的运算

    <script text="text/javascript">
        //4.基本数据类型的运算
        //遵循的规律：运算是从左往右; 任何类型的变量与string类型的变量拼接都会被强转为字符串
        //4.1 字符串的拼接
        var newName = name + '&' + family_name;
        console.log("newName:" + newName);

        //4.2 题目
        var  str1 = 10 + 10 + '10'; //2010
        var  str2 = '10' + 10 + 10; //101010
        var  str3 = (10 + '10') + 10;//101010
        console.log("str1:" + str1);
        console.log("str2:" + str2);
        console.log("str3:" + str3);
    </script>

 

4.数组及使用

<script text="text/javascript">
    //5.数组:可以装任意类型
    var numbers =[-10,'san',name,result,number,['a','b']];
    console.log(numbers)
    //5.1 遍历数组
    for (var i = 0; i<numbers.length ; i++){
        console.log('elementA:'+numbers[i]);
    }
    //5.2 JS中常用属性
    // 删除数组中最后一个内容
    numbers.pop();//出栈
    // 插入一个内容
    numbers.push('XMG');

    for (var i in numbers){
        console.log(i,numbers[i]);
    }

    //6.JS 常用的类库 Math
    var numsArr = [10,212,3223,32];
    //取最大值
    var maxNum = Math.max(210,21,10);
    //Math.max(numsArr); //不识别 Nan
    var newMax = Math.max.apply(this,numsArr);
    console.log(maxNum);
    console.log(newMax);

</script>