if (typeof someVar === 'undefined') { console.log('Undefined variable'); } else if (typeof someVar === 'null') { console.log('Null-value'); } This code also results in: Undefined variable Technically speaking, some_var is an undefined variable, as it has no assignment. On th...
In the above example, we have used the first if statement to check if the "a" variable is either undefined or null. If it satisfies either of the conditions, then the if block will execute; otherwise, the else block will execute. In the second statement, we have used the if statement ...
How to Check String is Empty or Not in Javascript? In this example, we use JavaScript to check string is empty or null using !str || str.trim().length === 0;. This expression evaluates to true if the string is empty or null, and false otherwise. You can check and edit this code...
我的检查方法有以下代码: static emptyOrWhiteSpaceString(obj: string, paramName: string) { if (obj === null || obj === '' || obj === ' ') { throw new ServiceException(`${paramName} name is empty.`); } } 我从一个评审员那里得到了这个建议: if (!obj || !obj.trim()) 我...
constructor === Object; value = null; // null value = undefined; // undefined Perfect, no error is thrown 😁# B. Empty Object Check in Older BrowsersWhat if you need to support older browsers? Heck, who am I kidding! We all know when I say older browsers, I'm referring to ...
var dark = typeof darkColor !== typeof undefined ? darkColor : "black"; Related Searches to JavaScript check if variable exists (is defined/initialized) - javascript tutorial javascript check if variable is declaredjavascript check if variable is nulljavascript check if variable has valuejavascript...
How to check if is null How to check if model property is empty in View page How to check if Session[“abc”] or viewdata[“abc”] is empty or have data? How to check if user has changed something in form's default value How to check if user is logged in how to check in my ...
Alternatively, it can also be used astypeof()methodin JavaScript. Syntax: typeof(variable); Example 1: str="This is my place.";if(typeofstr==String){console.log('The variable is a String.');}else{console.log('The variable is not a String.');} ...
let intVar = 2; let floatVar = 10.5; let stringVar = '4'; let nanVar = NaN; let infinityVar = Infinity; let nullVar = null; let undefinedVar = undefined; Using the Number.isFinite() function The Number.isFinite() function checks if the variable is a number, but also checks if...
flag = checkIsNULL(value); } if(flag&&value!=""){ flag = checkItem.fun(value); } if(flag == false){ if(checkItem.controlType == "checkBox" || checkItem.controlType == "radio"){ var _obj = document.getElementsByName(checkItem.id); ...