They are not equivalent. The first will execute the block following theifstatement ifmyVaristruthy(i.e. evaluates totruein a conditional), while the second will execute the block ifmyVaris any value other thannull. The only values that are not truthy in JavaScript are the following (a.k.a...
This tutorial teaches how to check if a variable is not null in JavaScript. if(myVar){...} This way will evaluate totruewhenmyVarisnull, but it will also get executed whenmyVaris any of these: undefined null 0 ""(the empty string) ...
To check if a value is an object, the above isObject() method does the following:Use the typeof operator to verify that the variable type is object— typeof obj === 'object'. Verify the value is not null— obj !== null. Use the Array.isArray() method to verify that the value ...
function doSomething(value) { if(typeof(value) === 'string') { console.log('value is a string') } else if(typeof(value) === 'number') { console.log('value is a number'); }else if(typeof(value) === 'object') { console.log('value is a object'); } } doSomething("string...
leta;if(typeofa ==='undefined') {console.log('The variable is undefined '); }elseif(typeofa ==='null') {console.log('The variable is Null-value'); } Output: Run Code Explanation: The typeof operator specifies the type of the variable. However, users should note that if they chuc...
// Undefined variableleta;if(a ==null) {console.log('Null or undefined value!'); }else{console.log(a); } This would check whetheraiseithernullorundefined. Sinceaisundefined, this results in: Null or undefined value! Though, we don't really know which one of these is it. If we were...
In JavaScript, a value can either be a primitive or an object. Therefore, you can check if a value is a JavaScript primitive (as opposed to being an object) using the following check: !(value instanceof Object) You may see value !== Object(value) as a means to check for prim...
JavaScript has 9 types in total: undefined boolean number string bigint symbol object null (typeof() shows as object) function (a special type of object) To verify if a variable is a number, we simply we need to check if the value returned by typeof() is "number". Let's try it ...
Ensure the value is notundefinedornullusingArray.prototype.includes(). Compare theconstructorproperty on the value withtypeto check if the provided value is of the specifiedtype. constis=(type,val)=>![,null].includes(val)&&val.constructor===type;// Examplesis(Array,[1]);// trueis(ArrayBuff...
document.getElementById("output").innerHTML = "Sting has some Value"; 14 } 15 } 16 Run Output of Js Check if string is empty Example 2 : React check if string is null or empty In this second example of this tutorial, we use React JS to check if a string is empty or null us...