It usually returns the variable type as a string object. There are standard return types to the typeof operator in javascript. string: typeof returns string for a variable type string. number: It returns number for a variable holding an integer or a floating-point value. boolean: For a ...
If you want to check whether a variable has been initialized or defined (i.e. test whether a variable has been declared and assigned a value) you can use the typeof operator.The most important reason of using the typeof operator is that it does not throw the ReferenceError if the ...
Thetypeofoperator returns object for all types of objects: objects arrays sets maps You cannot usetypeofto determine if a JavaScript object is an array or a date. How to Recognize an Array How to know if a variable is an array?
JavaScript provides several ways to check if a variable is a string. One of the most common methods is to use the typeof operator, which returns the type of a variable. For example, the following code checks if a variable named “myVar” is a string: if (typeof myVar === "string")...
How to check a not defined variable in javascript javascript里怎么检查一个未定义的变量? in JavaScript null is an object. There's another value for things that don't exist, undefined. The DOM returns null for almost all cases where it fails to find some structure in the document, but in ...
Please note that the instanceof operator returns "true" if a variable is initialized with the "new" keyword. Example: instanceof Copy var stringObj = new String(); var str = "this is str"; stringObj instanceof String; //returns true str instanceof String; //returns false Try it ...
Here's a Code Recipe to check whether a variable or value is either an array or not. You can use the Array.isArray() method. For older browser, you can use the polyfill 👍 constvariable=['🍝','🍜','🍲'];// ✅ NEWER BROWSERArray.isArray(variable);// 🕰 OLDER BROWSERObj...
How to check whether a variable is undefined or null? Method 1: Using the OR (||) operator to check undefined and null variable As discussed above, users can check if a variable is null or undefined using theOR (||)operator. It checks if the variable satisfies either of the two conditi...
let myString = new String("John Doe"); if (_.isString(myString)) { console.log("This variable is a string"); } else { console.log("This variable is not a string"); } Output: This variable is a string Conclusion In this article, we've learned how to check if a variable is...
In this tutorial, we'll be covering how to check if a variable is a number in JavaScript. We'll use the isNan(), typeOf() and isFinite() functions to do that.