JavaScript TypeError – Can’t redefine non-configurable property “x”

This JavaScript exception can’t redefine non-configurable property occurs if user tries to redefine a property, but that property is non-configurable.

Message:

TypeError: Cannot modify non-writable property {x} (Edge)
TypeError: can't redefine non-configurable property "x" (Firefox)
TypeError: Cannot redefine property: "x" (Chrome)

Error Type:

TypeError

Cause of the Error: If there is an attempt to redefine a property, but that property is non-configurable.

Example 1: In this example, the ‘prop1’ is being attempted to change the value, so the error has occurred.

Javascript

let GFG_Obj = Object.create({});
Object.defineProperty(GFG_Obj, "prop1", { value: "val1" });
Object.defineProperty(GFG_Obj, "prop1", { value: "val2" });

Output:

TypeError: Cannot modify non-writable property 'prop1'

Example 2: In this example, the ‘prop2’ is being attempted to change the value, So the error has occurred.

Javascript

let Obj = Object.create({ "prop1": "val1" });
Object.defineProperty(Obj, "prop2", { value: "val21" });
Object.defineProperty(Obj, "prop2", { value: "val22" });

Output:

TypeError: Cannot modify non-writable property 'prop2'