index.js

import waitForTrue from './waitForTrue'

export default waitForTrue

package.json

{
  "name": "waitForTrue",
  "version": "1.0.0"
}

waitForTrue.js

/**
 * @summary Function that wait for var be ready, and when its ready it will run the callback
 * @description Function will be reexecuted on setTimeOut until var is ready
 * when var exists the `callback` will be executed
 * the function usually runs by passing an global param as `variable` 
 *
 * @param { Function } fnIsTrue - The function that should return an boolean
 * @param { Function } callback - The callback function to be executed
 * @param { Number } time? - Optional time to try again
*/
function waitForTrue (fnIsTrue, callback, time) {
    if (fnIsTrue()) {
        return callback();
    }
    
    setTimeout(function() {
        waitForTrue(fnIsTrue, callback, time);
    }, time || 50);
}