Function: isDefined()
ts
function isDefined<T>(val): val is T;Checks if a value is defined (not undefined or null). 检查值是否已定义（非undefined或null）。
Type Parameters
| Type Parameter | Description |
|---|---|
T | The type of the value to check / 要检查的值的类型 |
Parameters
| Parameter | Type | Description |
|---|---|---|
val | T | null | undefined | The value to check / 要检查的值 |
Returns
val is T
True if the value is defined / 如果值已定义则返回true
Example
typescript
isDefined(1) // => true
isDefined('hello') // => true
isDefined(false) // => true
isDefined(0) // => true
isDefined('') // => true
isDefined([]) // => true
isDefined({}) // => true
isDefined(null) // => false
isDefined(undefined) // => false
isDefined(void 0) // => false
// Useful for filtering arrays
const arr = [1, null, 'test', undefined, 0]
const filtered = arr.filter(isDefined) // => [1, 'test', 0]Since
1.0.0