Random generator extension for VSCode

Question

Background

A VSCode extension that uses Chance.JS to generate random data types.

Concerns

1. My main concern is that there are 4 levels of function references that feels like a hack. From registerCommand → insertFunc* → randomFunc* → processSelection.
2. If the code is sensible TypeScript/JavaScript

The Code

export function activate(context: vscode.ExtensionContext) {
    context.subscriptions.push(vscode.commands.registerCommand('randomeverything.int', insertRandomInt));
    context.subscriptions.push(vscode.commands.registerCommand('randomeverything.letters', insertRandomLetters));
    context.subscriptions.push(vscode.commands.registerCommand('randomeverything.lettersAndNumbers', insertRandomLettersAndNumbers));
    context.subscriptions.push(vscode.commands.registerCommand('randomeverything.iPv4Address', insertRandomIPv4Address));
    context.subscriptions.push(vscode.commands.registerCommand('randomeverything.iPV6Address', insertRandomIPV6Address));
    /* More commands... */
}

function insertRandomInt(): void {

    var max:number;
    var min:number;

    Window.showInputBox({prompt: "Please enter [MIN-MAX]", value:"1-100"}).then(
        function(txt){
            if(txt){
                var args = txt.split("-");

                min = Number.parseInt(args[0]);
                max = Number.parseInt(args[1]);

                if(args.length != 2 || isNaN(min) || isNaN(max))
                {
                    Window.showErrorMessage("Invalid format.");
                    return;
                }
                processSelection(randomIntString, [min, max]);
            }
    });

}

function insertRandomLetters(): void {
    processSelection(randomLetters, []);
}

function insertRandomLettersAndNumbers(): void {
    processSelection(randomLettersAndNumbers, []);
}

function insertRandomIPv4Address(): void {
    processSelection(randomIP, ['ipv4']);
}

function insertRandomIPV6Address(): void {
    processSelection(randomIP, ['ipv6']);
}
/* More inserters... */

/**
 * Chance.js Wrappers
 */
function randomIntString(min, max): string {
    var chance = require('chance').Chance();
    var randomVar: Number = chance.integer({
      min: min,
      max: max
    });

    return randomVar.toString();
}

function randomIP(option?:string): string{
    var chance = require('chance').Chance();
    var randomVar:string;

    switch (option) {
        default:
        case 'ipv4':
            randomVar = chance.ip();
            break;
        case 'ipv6':
            randomVar = chance.ipv6();
            break;
    }

    return randomVar;
}

/* More wrappers... */

function processSelection(formatCB, argsCB) {

    let e = Window.activeTextEditor;
    let d = e.document;
    let sel = e.selections;

    e.edit(function (edit) {
        // iterate through the selections
        for (var x = 0; x < sel.length; x++) {
            let txt: string = d.getText(new Range(sel[x].start, sel[x].end));

            if (argsCB.length > 0) {
                txt = formatCB.apply(this, argsCB);
            } else {
                txt = formatCB();
            }

            //insert the txt in the start of the current selection
            edit.insert(sel[x].start, txt);
        }
    });
}

Answer 1

As for the architecture it seems good to me.

As for the TypeScript I have a few minor suggestions:

Avoid using var, use const or let instead.

function randomIntString(min: number, max: number): string {
    const chance = require('chance').Chance();
    const randomVar: number = chance.integer({
      min: min,
      max: max
    });

    return randomVar.toString();
}

It is also preferable to use let for for-cycle control variables.

for (let x = 0; x < sel.length; x++) {
   // body
}

It would help readability and maintainability if you specified the types of all the arguments of all your functions.

function randomIntString(min: number, max: number): string {
    // body
}

Also prefer using lower case type names for built-in primitive types (e. g. number over Number) when specifying the type of something.

You could specify the IP option type more precisely (asuming you use TypeScript >= 2.0). This will help you prevent typos and also improves readability (the code is more self-documenting):

type IpAddressType = 'ipv4' | 'ipv6';
function randomIP(option?: IpAddressType): string{
    // body stays the same
}

When the property of the object being initialized has the same name as the variable assigned to it you can shorten it like so (see the chance.integer call):

var randomVar: number = chance.integer({
      min,
      max
    });