Disallow Shadowing of Variables Inside of catch (no-catch-shadow)

In IE 8 and earlier, the catch clause parameter can overwrite the value of a variable in the outer scope, if that variable has the same name as the catch clause parameter.

var err = "x";

try {
    throw "problem";
} catch (err) {

}

console.log(err)    // err is 'problem', not 'x'

Rule Details

This rule is aimed at preventing unexpected behavior in your program that may arise from a bug in IE 8 and earlier, in which the catch clause parameter can leak into outer scopes. This rule will warn whenever it encounters a catch clause parameter that has the same name as a variable in an outer scope.

Examples of incorrect code for this rule:

/*eslint no-catch-shadow: "error"*/

var err = "x";

try {
    throw "problem";
} catch (err) {

}

function err() {
    // ...
};

try {
    throw "problem";
} catch (err) {

}

Examples of correct code for this rule:

/*eslint no-catch-shadow: "error"*/

var err = "x";

try {
    throw "problem";
} catch (e) {

}

function err() {
    // ...
};

try {
    throw "problem";
} catch (e) {

}

When Not To Use It

If you do not need to support IE 8 and earlier, you should turn this rule off.

Version

This rule was introduced in ESLint 0.0.9.

Resources

• Rule source
• Documentation source