This JavaScript exception is read-only works in strict mode-only and It occurs if a global variable or object property which has assigned to a value, is a read-only property.
Message:
TypeError: Assignment to read-only properties is not allowed in strict mode (Edge) TypeError: "x" is read-only (Firefox) TypeError: 0 is read-only (Firefox) TypeError: Cannot assign to read only property 'x' of #<Object> (Chrome) TypeError: Cannot assign to read only property '0' of [object Array] (Chrome)
Error Type:
TypeError
Cause of Error: The global variable or object property that has assigned value is a read-only property. You can not write data in those variables.
Example 1: In this example, any property of GFG_Obj can not be modified.
Javascript
'use strict';let GFG_Obj = Object.freeze({ prop1: 'val1', prop2: 'val2' });GFG_Obj.prop2 = 0; // TypeError |
Output(in console):
TypeError: Assignment to read-only properties is not allowed in strict mode
Example 2: In this example, the value of Math.PI can not be changed(Which is read-only).
Javascript
'use strict';Math.PI = 5; |
Output(in console):
TypeError: Assignment to read-only properties is not allowed in strict mode
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