let myString = "John Doe"; if (typeof myString === "string") { console.log("This variable is a string"); } else { console.log("This variable is not a string"); } Indeed, the myString is a string: This variable is a string Note: Even if the variable contains a number th...
To check if a variable is a string in React.js, you can use the typeof operator and compare it with the string literal 'string'. For example, you can write typeof variable === 'string' to check if variable is a string. This expression evaluates to true i
The typeof operator can be used to check if a variable is undefined by comparing its type with the string ‘undefined’. Here is an example of the code. let a; console.log(typeof a === 'undefined'); // true This method is safe because it won’t throw an error if the variable ...
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 } ...
Here we take an undefined variable name and compare it withvoid 0. This method also throws an error if we try to compare a variable that is not declared. Use thetypeofOperator to Check Undefined in JavaScript This operator returns a string that tells about the type of the operand. If the...
We can also check if a variable stores a truthy value. Truthful values are all values that are not false. Falsy values in JavaScript are:undefined,null,false, ,0,""(empty string),NaN(not a number). import{useEffect, useState}from'react'; ...
After iterating all the characters in a string, we will perform a conditional check to know if the value inside theallUpperCasevariable is true or not. If it istrue, all the characters in the string are in uppercase format. Output: ...
Check if a string is null or empty in XSLT 多条件查询 string.Format("/root/deviceList//item/guid[{0}]", strBuilder.ToString()) "/root/deviceList//item/guid[text()=\"h\" or text()=\"a\" or text()=\"c\"]"谓词嵌套var nodes = xmlDoc.SelectNodes(string.Format("/root/device...
The Number.isFinite() function checks if the variable is a number, but also checks if it's a finite value. Therefore, it returns false on numbers that are NaN, Infinity or -Infinity. Let's test it out on the variables we've defined above: > Number.isFinite(intVar); true > Number...
JavaScript offers many ways to check if a string contains a substring. Learn the canonical way, and also find out all the options you have, using plain JavaScript