Node.js async.whilst() is not executing at all

Question

I'm just trying to use async.whilst() as seen here.

Here is my simple code, taken from their docs:

var async = require('async');

console.log('start');
async.whilst(
  function () { return true; },
  function (callback) {
    console.log('iteration');
    callback();
  },
  function (err) {
    console.log('end');
  },
);

When I run this, the loop doesn't run. Only start is printed out.

Answer 1

Because you are returning true, that why the callback for function 1 wasn't called. So you only see the 'start'. You can find some information below:

    const async = require('async');
    let count = 0;
    const compareVariable = 10;
    console.log('start');
    async.whilst(
        function functionName1(callbackFunction) {
            // perform before each execution of iterFunctionInside, you need a condition(or other related condition) in 2nd params.
            callbackFunction(null, count < compareVariable)
        },
        // this func is called each time when functionName1 invoked
        function iterFunctionInside(callback) {
            // increase counter to compare with compareVariable
            count++;
            console.log('iteration', count);
            // if you want to show like tick time, you can set timeout here or comment out if you dont want
            setTimeout(() => {
                callback(null, count);
            }, 1000)
        },
        function (err, n) {
            console.log('end');
        },
    );