TS union type

TS Joint type

Joint type That is, through the pipeline | Set variables to multiple types , The assignment can be made according to the type of setting .

1 Common variable declaration

let res: number|string|boolean
res = 12
res = ' Xiao Xu '
res= true
// Only the specified type can be assigned , If other types are assigned, an error will be reported .

2 Array declaration uses

let arr: number[]|string[]
arr = [1,2]
arr = ['xiao','xu']

3 Use in a function

const test = (p: string | number) => {
     ... }