I'm using js-cookie alongside with typescript and I'm getting stuck with types while trying to parse a cookie item:
// the item 'number' contains a javascript number (ex:5)
let n:number
if(typeof Cookies.get('number')!== 'undefined'){
n = JSON.parse(Cookies.get('number'))
}else{
n = 0
}
Typescript: Argument of type 'string | undefined' is not assignable to parameter of type 'string'. Type 'undefined' is not assignable to type 'string'
I'm following the basic example of typescript documentation: https://www.typescriptlang.org/docs/handbook/2/narrowing.html
Am I making something wrong with this code snippet ?
You have two calls of Cookies.get('number'). Typescript can not know that the same value is returned for both calls.
Therefore, save the value in a variable:
let n:number
let value = Cookies.get('number')
if(typeof value !== 'undefined'){
n = JSON.parse(value)
}else{
n = 0
}