Prefer that
for-in loops should include an if statement JS-0051
Anti-pattern
Minor
8 months ago
—
8 months old
Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
49 fs.readFileSync(path.join(process.cwd(), 'wafRules.json')).toString()
50 )
51
52 for (const key in this.types) { 53 this.types[this.types[key]] = key 54 } 55 rulesJson.forEach((rule: _Rule) => {
56 this.rules[rule.id] = {
57 reg: new RegExp(rule.reg),
Description
Looping over objects with a for in loop will include properties that are inherited through the prototype chain.
This behavior can lead to unexpected keys in your for loop.
Bad Practice
for (const key in foo) {
doSomething(key);
}
Recommended
for (const key in foo) {
if (Object.prototype.hasOwnProperty.call(foo, key)) {
doSomething(key);
}
}
for (const key of Object.keys(foo)) {
doSomething(key);
}