Let's suppose I wrote the following code snipped in VSC:

let a = [1,2,3,4,5];
console.log(Math.max(...a))

If you hover over max, VSC gives you it's definition as:

(method) Math.max(...values: number[]): number
Returns the larger of a set of supplied numeric expressions.

@param values — Numeric expressions to be evaluated.

Screenshot of the definition

What does (...values: number[]): number mean? Does that mean that it takes in an array and stores it as an array called number[] internally? Also, what does @param values mean?

CodePudding user response：

What does (...values: number[]): number mean?

This uses rest parameter syntax, and just means that all of the parameters are of the same type: number. The return type of the function is also number.

This syntax value: type comes from TypeScript.

Does that mean that it takes in an array and stores it as an array called number[] internally?

If you were to implement Math.max yourself using this signature, then yes, all of the arguments passed to the function would be stored in a variable called values, which would be an array of numbers.

Also, what does @param values mean?

This is JSDoc syntax, and it refers to a function parameter.

CodePudding user response：

What does (...values: number[]): number mean?

It means it's a function that takes as many numbers as you want, each as separate parameters (ie, you can call Math.max(1, 2), or Math.max(1, 2, 3, 4, 5, 6), etc), and it returns a number

Does that mean that it takes in an array and stores it as an array called number[] internally?

No, it says nothing about the internal implementation, and no array needs to be involved. It's just telling you how you can use this function

Also, what does @param values mean?

To a human, it just means "this function takes a parameter called values". Some automated tools look for the keyword @param as part of JSDoc