1、强制数据类型转换
1-1String,Boolean—>number
1-1-1、纯数字String—>number
特点:只能识别纯数字的字符串
Number(value)
var a = "10";
var str = "hello"
console.log(Number(a)) //10
console.log(Number(str)) //NaN 不是一个数字
console.log(Number("3.0")) //3
console.log(Number(undefined)) // NaN
1-1-2、Boolean—>number
var t = true
var f = false
console.log(Number(t)); //1
console.log(Number(f)); //0
1-1-3、含有字符的String—>Number
parseInt()
parseFloat()
var str = "12px"
var s = "12.34px"
console.log(parseInt(str));
console.log(parseFloat(s));
1-2number,String—>Boolean
1-2-1、number—boolean
Boolean()
0转换为false,其他都为true
1-2-2、string—>boolean
""为false,其他都为true
1-3、Any—>String
String()
toString()
+""