In strict mode, read-only variables cannot be assigned

• STRICT_MODE_ASSIGN_TO_READONLY_VAR
• Error
• High
• No tags

This rule applies when a value is assigned to read-only variables in strict mode.

The read-only variables are as follows:

1. import bindings
2. Predefined global variables such as undefined, NaN, Infinity

Any assignment to the above variables that silently fails in normal code will throw a TypeError exception in strict mode.

Note: Applied for module code without "use strict" directive since module code is always strict mode code.

Noncompliant Code Example

// Example 1
import { A } from 'a';
A = 1; // STRICT_MODE_ASSIGN_TO_READONLY_VAR alarm because it is module code.

// Example 2
'use strict';
undefined = 1; // STRICT_MODE_ASSIGN_TO_READONLY_VAR alarm
NaN = 2; // STRICT_MODE_ASSIGN_TO_READONLY_VAR alarm
Infinity = 3; // STRICT_MODE_ASSIGN_TO_READONLY_VAR alarm

Version

This rule was introduced in DeepScan 1.0.0-alpha.

See

• Strict mode