disallow reassigning exceptions in catch clauses (no-ex-assign)

The "extends": "eslint:recommended" property in a configuration file enables this rule.

If a catch clause in a try statement accidentally (or purposely) assigns another value to the exception parameter, it impossible to refer to the error from that point on. Since there is no arguments object to offer alternative access to this data, assignment of the parameter is absolutely destructive.

Rule Details

This rule disallows reassigning exceptions in catch clauses.

Examples of incorrect code for this rule:

/*eslint no-ex-assign: "error"*/

try {
    // code
} catch (e) {
    e = 10;
}

Examples of correct code for this rule:

/*eslint no-ex-assign: "error"*/

try {
    // code
} catch (e) {
    var foo = 10;
}

Further Reading

• The “catch” with try…catch by Ben Alman explains how the exception identifier can leak into the outer scope in IE 6-8

Version

This rule was introduced in ESLint 0.0.9.

Resources

• Rule source
• Documentation source