(一)联合类型: |
let result: (string | number) = 'hh'
(二) 函数可选参数需要加 ?
function getName (age: number, name?:string):string {
return `age: ${age}, name: ${name}`
}
如果指定了默认值,就不用加 ?了
function getName (age: number, name:string = 'xiaoming'):string {
return `age: ${age}, name: ${name}`
}
剩余参数数组,以及默认值 undefined 占位
function getName (age: number, name:string = 'xiaoming', ...args:Array<number>):void {
console.log(`age: ${age}, name: ${name}`)
for (let item of args) {
console.log(item)
}
}
getName(13, undefined, 34, 4, 5)
(三)一般的DOM都设置成any,因为不知道是什么DOM类型
let oButton:any = document.getElementById('btn')
(四)localStorage 如果没取到,值是 null
let age: (string | null) = localStorage.getItem('age')
console.log(age)
所以代码要这样写