type checking techniques #types #vanillajs

typecheck-1.js

//src: https://vanillajstoolkit.com/helpers/truetypeof/

/*!
 * More accurately check the type of a JavaScript object
 * (c) 2018 Chris Ferdinandi, MIT License, https://gomakethings.com
 * @param  {Object} obj The object
 * @return {String}     The object type
 */
var trueTypeOf = function (obj) {
	return Object.prototype.toString.call(obj).slice(8, -1).toLowerCase();
};

 console.log( trueTypeOf([]) ); //"array"

typecheck-2.js

var elemCheck = {};   

    elemCheck.isArray = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Array';
    }

    elemCheck.isObject = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Object';
    }

    elemCheck.isString = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'String';
    }

    elemCheck.isDate = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Date';
    }

    elemCheck.isRegExp = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'RegExp';
    }

    elemCheck.isFunction = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Function';
    }

    elemCheck.isBoolean = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Boolean';
    }

    elemCheck.isNumber = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Number';
    }

    elemCheck.isNull = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Null';
    }

    elemCheck.isUndefined = function(elem) {
        return Object.prototype.toString.call(elem).slice(8,-1) === 'Undefined';
    }



    console.log( elemCheck.isArray([]) );
    console.log( elemCheck.isObject({}) ); // true
    console.log( elemCheck.isString('') ); // true
    console.log( elemCheck.isDate(new Date()) ); // true
    console.log( elemCheck.isRegExp(/test/i) ); // true
    console.log( elemCheck.isFunction(function () {}) ); // true
    console.log( elemCheck.isBoolean(true) ); // true
    console.log( elemCheck.isNumber(1) ); // true
    console.log( elemCheck.isNull(null) ); // true
    console.log( elemCheck.isUndefined() ); // true

typecheck-3.md

type checking techniques widely used and not using Object.prototype.toString.call(obj).slice(8, -1) trick

check if an object is an array with vanilla JavaScript

https://gomakethings.com/how-to-check-if-an-object-is-an-array-with-vanilla-javascript/