forin.md

Pattern: Unfiltered for ... in

Issue: -

Description

Requires a for ... in statement to be filtered with an if statement.

Rationale:

for (let key in someObject) {
    if (someObject.hasOwnProperty(key)) {
        // code here
    }
}

This prevents accidental iteration over properties inherited from an object’s prototype.

Further Reading

• TSLint - forin
• MDN web docs - for...in