Introduction to tslib

tslib is a runtime library for TypeScript that contains all of the TypeScript helper functions. This library is especially useful when you need to reduce the output JavaScript file size and reuse common TypeScript functionalities.

Key Features and APIs of tslib

__extends

The __extends function is used to support class inheritance in TypeScript.

var __extends = (this && this.__extends) || function (d, b) {
    extendStatics(d, b);
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};

__assign

The __assign function is utilized to assign the properties of one or more source objects to a target object.

var __assign = (this && this.__assign) || Object.assign || function (t) {
    for (var s, i = 1, n = arguments.length; i < n; i++) {
        s = arguments[i];
        for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p))
            t[p] = s[p];
    }
    return t;
};

__rest

The __rest function is used to create a shallow copy of an object, excluding specified properties.

var __rest = (this && this.__rest) || function (s, e) {
    var t = {};
    for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)
        t[p] = s[p];
    if (s != null && typeof Object.getOwnPropertySymbols === "function")
        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) {
            if (e.indexOf(p[i]) < 0) t[p[i]] = s[p[i]];
        }
    return t;
};

__decorate

The __decorate function is used to add decorators to classes and class members.

var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r)) || r;
    return c > 3 && r && Object.defineProperty(target, key, r), r;
};

Practical Example: Building a Simple App

Let's look at a simple application example which uses some of the APIs described above:

Example App: User Manager

class UserManager {
    private __users: User[] = [];

    addUser(user: User): void {
        this.__users = __assign([], this.__users, [user]);
    }

    getUser(id: number): User | undefined {
        return this.__extends(this.__users.find(user => user.id === id), null);
    }

    removeUser(id: number): void {
        this.__users = __rest(this.__users, [id]);
    }
}

class User {
    constructor(public id: number, public name: string) {}
}

// Usage
const manager = new UserManager();
manager.addUser(new User(1, 'John Doe'));
console.log(manager.getUser(1));
manager.removeUser(1);
console.log(manager.getUser(1));

By leveraging the tslib utility functions, this example showcases efficient object manipulation and inheritance in TypeScript.

Hash: 73d21c2a7fcc2a5741f740b9320733dfd302725b2ca4213fa919b1977e2bca59