这里整理了Object和Number扩展方法。
<!DOCType html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<script>
console.log("-------------- number 扩展 --------------");
{
// Number.EPSILON 是 JS最小精度
console.log(Number.EPSILON); //2.220446049250313e-16
console.log(0.1 + 0.2); //0.30000000000000004
function equal(a, b) {
return Math.abs(a - b) < Number.EPSILON;
}
console.log(equal(0.1 + 0.2, 0.3)); //true
//1. 二进制和八进制
//0b：二进制
//0o：八进制
//0x：十六进制
console.log(0b111110111); // 503
//2. Number.isFinite 检查一个值是否为有限的
console.log(Number.isFinite(15)); //true
console.log(Number.isFinite(Infinity)); //false
//3. Number.isNaN 检查一个值是否为NaN
console.log(Number.isNaN(123)); //false
console.log(Number.isNaN(NaN)); //true
//4. Number.paresInt
console.log(Number.parseInt('12.34')); //12
console.log(Number.parseFloat('12.34aa')); //12.34
//5. Number.isInteger
console.log(Number.isInteger(25)); //true
console.log(Number.isInteger(2.5)); //false
//6. Math.trunc 将数字的小数部分去掉
console.log(Math.trunc(3.5)); //3
//7. Math.sign 判断一个数 正数，负数 或 零
console.log(Math.sign(-5)); //-1
console.log(Math.sign(0)); //0
console.log(Math.sign(5)); //1
}
console.log("-------------- object方法 扩展 --------------");
{
//1. Object.is(value1, value2) 判断两个值是否严格相等
console.log(Object.is(10, 10)); //true
console.log(Object.is(+0, -0)); //false
console.log(Object.is(NaN, NaN)); //true
console.log(NaN === NaN); //false
//2. Object.assign(target, ...sources) 合并多个对象
const config1 = {
host: 'localhost',
port: 8080,
name: 'test',
password: '123456',
test1: 'aaa',
}
const config2 = {
host: '192.168.1.1',
port: 3306,
name: 'root',
password: '1111',
test2: 'bb'
}
//后面的覆盖前面的
let config = Object.assign(config1,config2);
console.log(config);//{host: '192.168.1.1', port: 3306, name: 'root', password: '1111', test1: 'aaa', test2: 'bb'}
//3. Object.setPrototypeOf Object.getPrototypeof
const school ={
name:'小学'
}
const cities = {
area: ['海淀', '朝阳', '顺义']
}
Object.setPrototypeOf(school, cities);
console.log(school); // {area: Array(3), name: "小学"}
console.log(Object.getPrototypeOf(school)); // {area: Array(3)}
}
</script>
</body>
</html>
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