Client - isNullOrEmpty Extension for String Values

note

In TypeScript, it is necessary to define (export default class Form1 extends Form.Designer { }) outside the form class. The string can then be used in variables as variable.isNullOrEmpty()**.

'''js declare global { interface String { isNullOrEmpty(this: any): boolean; } }

String.prototype.isNullOrEmpty = function (this: any): boolean { return isNullOrEmpty(this); };

function isNullOrEmpty(value : any) : boolean { return value === undefined || value === null || value === ""; }