JavaScript Define a Function to Check If a Variable is a String 6 7 8 9 // Defining a function 10 function isString(myVar) { 11 return (typeof myVar === 'string'); 12 } 13 14 // Sample variables 15 var x = 10; 16 var y = true; 17 var z = "...
Methods to Check if a Variable is Undefined Using typeof Operator Using Strict Equality (===) Using Loose Equality (==) Using the void Operator Using a Custom Utility Function This article covers different ways to check if a variable is undefined, helping you write code that handles these ...
str = "This is my place."; if (typeof str == String) { console.log('The variable is a String.'); } else { console.log('The variable is not a String.'); } Output:The variable is not a String. Example 2:str = "That is your place."; if (typeof(str) === 'string') {...
// Check if variable is equal to value if (username === "sammy_shark") { console.log(true); } 输出: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 true 如前所述,变量可以用来表示任何JavaScript数据类型。在本例中,我们将使用字符串、数字、对象、布尔值和null值声明变量。 代码语言:javascr...
// Sample variablevarmyVar='Hello';// Test if variable is a stringif(typeofmyVar==='string'){alert('It is a string.');}else{alert('It is not a string.');} You can also define a custom function to check whether a variable is a string or not. ...
Variable Scope Solution 2: We can use typeofoperatorto check the variable is defined or not. if (typeof variable !== 'undefined') { // the variable is defined } Solution 3: You can use this code: if (typeof variable === 'undefined') { // variable is undefined } ...
One of the simplest ways to check if a variable is undefined is by using the typeof operator. This operator returns a string that indicates the type of the unevaluated operand. If the variable is not defined, typeof will return the string “undefined”. Here’s how you can use it: let...
Checking if Boolean Is Primitive or ObjectA boolean literal (i.e. true or false) is a primitive. You can check this using the custom isPrimitive() function: console.log(isPrimitive(true)); // true console.log(isPrimitive(false)); // true ...
4, 5]; let str = "Tutorialspoint"; document.getElementById('array') .innerHTML= "Variable: " +arr +"" +"Variable: " +str; function checkArray() { let res1 = Array.isArray(arr); let res2 = Array.isArray(str); document.getElementById("result") .innerHTML = "Is it array?:...
Javascript Boolean Type Introduction Using the typeof operator, we can check the datatype of a variable. If the variable is a Boolean value, typeof will return the string 'boolean'. Copy vara =Boolean(true);varb = false;//www.java2s.comvarc ="";vard = newDate();if(typeofa ==='...