JavaScript SyntaxError - Applying the 'delete' operator to an unqualified name is deprecated Last Updated : 15 Jul, 2025 Comments Improve Suggest changes Like Article Like Report This JavaScript exception applying the 'delete' operator to an unqualified name is deprecated works in strict mode and it occurs if variables are tried to be deleted with the delete operator. Message: SyntaxError: Calling delete on expression not allowed in strict mode (Edge) SyntaxError: applying the 'delete' operator to an unqualified name is deprecated (Firefox) SyntaxError: Delete of an unqualified identifier in strict mode. (Chrome) Error Type: SyntaxError Cause of Error: In strict mode, trying to delete a variable will throw an error and is not permitted. Normal variables in JavaScript can't be deleted with the help of the delete operator. Example 1: JavaScript 'use strict'; let GFG = "This is GeeksforGeeks"; console.log(GFG); GFG = null; Output: This is GeeksforGeeks Example 2: In this example, the delete operator is used which causes the error. JavaScript 'use strict'; let GFG = "This is GeeksForGeeks"; console.log(GFG); delete GFG; Output(in console): SyntaxError: Delete of an unqualified identifier in strict mode. Comment More infoAdvertise with us P PranchalKatiyar Follow Improve Article Tags : JavaScript Web Technologies JavaScript-Errors Explore JavaScript Tutorial 8 min read JavaScript BasicsIntroduction to JavaScript 4 min read JavaScript Versions 2 min read How to Add JavaScript in HTML Document? 3 min read JavaScript Syntax 6 min read JavaScript Output 4 min read JavaScript Comments 2 min read JS Variables & DatatypesVariables and Datatypes in JavaScript 6 min read Global and Local variables in JavaScript 4 min read JavaScript Let 6 min read JavaScript const 5 min read JavaScript Var Statement 7 min read JS OperatorsJavaScript Operators 5 min read Operator precedence in JavaScript 2 min read JavaScript Arithmetic Operators 5 min read JavaScript Assignment Operators 5 min read JavaScript Comparison Operators 5 min read JavaScript Logical Operators 5 min read JavaScript Bitwise Operators 5 min read JavaScript Ternary Operator 4 min read JavaScript Comma Operator 2 min read JavaScript Unary Operators 4 min read JavaScript in and instanceof operators 3 min read JavaScript String Operators 3 min read JS StatementsJavaScript Statements 4 min read JavaScript if-else 3 min read JavaScript switch Statement 4 min read JavaScript Break Statement 2 min read JavaScript Continue Statement 1 min read JavaScript Return Statement 4 min read JS LoopsJavaScript Loops 3 min read JavaScript For Loop 4 min read JavaScript While Loop 3 min read JavaScript For In Loop 3 min read JavaScript for...of Loop 3 min read JavaScript do...while Loop 4 min read JS Perfomance & DebuggingJavaScript | Performance 4 min read Debugging in JavaScript 4 min read JavaScript Errors Throw and Try to Catch 2 min read JS ObjectObjects in Javascript 4 min read Object Oriented Programming in JavaScript 3 min read JavaScript Objects 6 min read Creating objects in JavaScript 5 min read JavaScript JSON Objects 3 min read JavaScript Object Reference 4 min read JS FunctionFunctions in JavaScript 4 min read How to write a function in JavaScript ? 4 min read JavaScript Function Call 2 min read Different ways of writing functions in JavaScript 3 min read Difference between Methods and Functions in JavaScript 3 min read Explain the Different Function States in JavaScript 3 min read JavaScript Function Complete Reference 3 min read JS ArrayJavaScript Arrays 7 min read JavaScript Array Methods 7 min read Best-Known JavaScript Array Methods 6 min read Important Array Methods of JavaScript 7 min read JavaScript Array Reference 4 min read Like