typeof
- 可以返回数据类型
console.log(typeof 'hszz') //string
instanceof
- 判断对象实例是否属于某个类型
let o = function(name) {
this.name = name
}
let o1 = new o('hszz')
console.log(o1 instanceof o) // true
toString split reverse join
- toString 数字转化为字符串
- split 将字符串切割为数组
- reverse 倒装数组
- join 将字符串拼接为字符串
let x = 123
x = x.toString()
console.log(typeof x)
x = x.split('')
console.log(x)
x = x.reverse()
console.log(x)
x = x.join('')
console.log(x)
Math.ceil()
- Math.ceil() 函数返回大于或等于一个给定数字的最小整数。
console.log(Math.ceil(.95)); // 1
console.log(Math.ceil(4)); // 4
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Math/ceil
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