JavaScript类型系统之布尔Boolean类型详解

var b1 = true;
var b2 = new Boolean(true);
console.log(b1,typeof b1);//true 'boolean'
console.log(b2,typeof b2);//Boolean{[[PrimitiveValue]]: true} 'object'
console.log(b1.valueOf(), typeof b1.valueOf());//true 'boolean'
console.log(b2.valueOf(), typeof b2.valueOf());//true 'boolean'

if(a > 1){
//条件为true时，执行此处
}else{
//条件为false时，执行此处
}

console.log(!!1);//true
console.log(!!0);//false
console.log(!!' ');//true
console.log(!!'');//false

console.log( 1 > 2);//false
console.log( 1 < 2);//true

console.log(Boolean(undefined));//false
console.log(Boolean(null));//false
console.log(Boolean(0));//false
console.log(Boolean(-0));//false
console.log(Boolean(NaN));//false
console.log(Boolean(''));//false
console.log(Boolean(false));//false

console.log(Number(''));//0
console.log(Number(' '));//0
console.log(Boolean(''));//false
console.log(Boolean(' '));//true

console.log(Boolean({}));//true
console.log(Boolean([]));//true
console.log(Boolean(new Boolean(false)));//true
console.log(Boolean(false));//false
console.log(Boolean(new Boolean(null)));//true
console.log(Boolean(null));//false

console.log(true.valueOf());//true
console.log(true.toString());//'true'
console.log(true.toLocaleString());//'true'
console.log(Boolean(false).valueOf());//false
console.log(Boolean(false).toString());//'false'
console.log(Boolean(false).toLocaleString());//'false'