js 数据类型转换

var n1 = 123;
var n2 = ‘123‘;
var n3 = n1+n2;
// 隐式转换
console.log(typeof n3);

var str1 = String(n1);
console.log(typeof str1);

var num = 234;
console.log(num.toString())

var  stringNum = ‘789.123wadjhkd‘;
var num2 =  Number(stringNum);
console.log(num2)

// parseInt()可以解析一个字符串 并且返回一个整数
console.log(parseInt(stringNum))
console.log(parseFloat(stringNum));

var b1 = ‘123‘;  真
var b2 = 0;      假
var b3 = -123    真

var b4 = Infinity;  真   特殊的number  
var b5 = NaN;       假   特殊的number 

var b6=undefined 假
 var b7 = null;   假

// 非0既真 console.log(Boolean(b7))