I'm doing a typescript tutorial exercise that wants me to change an any[] array into string[].
// declaring an array of any datatype
const manufacturers: any[] = [{ id: 'Samsung', checked: false },
{ id: 'Motorola', checked: false },
{ id: 'Apple', checked: false },
{ id: 'Sony', checked: false }
];
console.log('Available Products are: ');
// logic to populate the above declared array's id value
for (const item of manufacturers) {
console.log(item.id);
if(item.id === "Apple")
{
console.log("check value is " + item.checked)
}
}
The above one works, but if I change any[] into string[], it doesn't work. If I do
"const manufacturers: [string,boolean][]="
then it recognizes the boolean and not the string. I'm trying to understand why it doesn't see id as a string variable and make it match. How do I accomplish this without using 'any[]'
The type of manufacturers is { id: string, checked: boolean }[].
Explanation:
The manufacturers object is an array, containing objects. Each object has an id and a checked property which are of types string and boolean respectively.
So as you said, changing from any[] to string[] won't work, because the manufacturers type is not string[], but { id: string, checked: boolean }[].
const manufacturers: { id: string, checked: boolean }[] = [{ id: 'Samsung', checked: false },
{ id: 'Motorola', checked: false },
{ id: 'Apple', checked: false },
{ id: 'Sony', checked: false }
];
console.log('Available Products are: ');
for (const item of manufacturers) {
console.log(item.id);
if (item.id === "Apple") {
console.log("check value is " + item.checked)
}
}
As @Calz pointed out, you don't need to explicitly enter the type of the variable, as initialization is taking place at the time of declaration.
Here's a small example explaining this:
let a;
a = 5
console.log(typeof a) // number
a = "string"
console.log(typeof a) // string
let b = 5
b = "some string"; // error as TypeScript blames that type string is not assignable to type number