1.字符串转换成数字
//String 转换成Number.
var msg = "汉字";
var n1 = Number(msg);
console.log(n1);
//NaN
console.log(Number('100'));
// 转number之前会去掉左右的空格，去掉之后再转换。
console.log(Number('100'));
console.log(Number(' 101 '));
console.log(Number(' 101 '));
console.log(Number(' 1 01 '));//NaN 只会去掉前后的空格。
console.log(Number(''));//0
console.log(Number(' '));//0
console.log("-----");
//parseInt在字符串中提取不到数字就认为是NAN
console.log(parseInt('100'));
console.log(parseInt(' 101 '));//101
console.log(parseInt(' 101 '));//101
console.log(parseInt(' 1 01 '));//1
console.log(parseInt(''));//NAN
console.log(parseInt(' '));//NAN
//boolean转换成Number
console.log("-----");
//boolean转换成Number
var num1 = Number(true);
var num2 = Number(false);
var num3 = Number(null);
var num4 = Number(undefined);
console.log(num1);//1
console.log(num2);//0
console.log(num3);//0
console.log(num4);//NAN
Number和parseInt的对比------ parseInt在字符串中提取不到数字就认为是NAN
console.log(Number(true));//1
console.log(Number(false));//0
console.log(Number(null));//0
console.log(Number(undefined));//NAN
console.log(parseInt(true));//NAN
console.log(parseInt(false));//NAN
console.log(parseInt(null));//NAN
console.log(parseInt(undefined));//NAN
2.其他类型转换成字符串
//其他类型转换成字符串
//数字转换成字符串
var string1 = String("10");
console.log(string1);//10
var string2 = String(true);
console.log(string2);//true
var string3 = String(false);
console.log(string3);//false
var string4 = String(NaN);
console.log(string4);//NaN
var string5 = String(null);
console.log(string5);//null
var string6 = String(undefined);
console.log(string6);//undefined
3.其他类型转换成boolean类型
//1.数字转换成boolean,
//0 null NAN undefined可以转换成false 其他都是true
var b1 = Boolean(23.0);
var b2 = Boolean(-23.0);
var b3 = Boolean(0);
var b4 = Boolean(NaN);
var b5 = Boolean(null);
var b51 = Boolean(undefined);
var b6 = Boolean(Infinity);
var b7 = Boolean(-Infinity);
console.log(b1);//true
console.log(b2);//true
console.log(b3);//false
console.log(b4);//false
console.log(b5);//false
console.log(b51);//false
console.log(b6);//true
console.log(b7);//true
//2.字符串转换成boolean
//除了空字符串是false 其他都是true
var b11 = Boolean(" 111djkdjkjfk ");
console.log(b11);//true
var b11 = Boolean(" ");//空字符串也认为是true
console.log(b11);//true
var b11 = Boolean(""); //字符串没有值返回false.
console.log(b11);//false
隐式类型转换 是强制类型转换，Number() String() Boolean()
