How do I write an extension method in JavaScript?

Question

I need to write a few extension methods in JS. I know just how to do this in C#. Example:

public static string SayHi(this Object name)
{
    return \"Hi \"         


        

Answer 1

Using Global augmentation

declare global {
    interface DOMRect {
        contains(x:number,y:number): boolean;
    }
}
/* Adds contain method to class DOMRect */
DOMRect.prototype.contains = function (x:number, y:number) {                    
    if (x >= this.left && x <= this.right &&
        y >= this.top && y <= this.bottom) {
        return true
    }
    return false
};