Prefer that
for-in loops should include an if statement JS-0051
Anti-pattern
Minor
5 months ago
—
6 months old
Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
3544 (e._getDelegateConfig = function () {
3545 var t = {};
3546 if (this.config)
3547 for (var e in this.config)3548 this.constructor.Default[e] !== this.config[e] &&3549 (t[e] = this.config[e]);3550 return t;
3551 }),
3552 (e._cleanTipClass = function () {Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
1246 function (t) {
1247 for (var e = 1; e < arguments.length; e++) {
1248 var n = arguments[e];
1249 for (var i in n)1250 Object.prototype.hasOwnProperty.call(n, i) && (t[i] = n[i]);1251 }
1252 return t;
1253 };Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
39 function (t) {
40 for (var e = 1; e < arguments.length; e++) {
41 var n = arguments[e];
42 for (var i in n) 43 Object.prototype.hasOwnProperty.call(n, i) && (t[i] = n[i]); 44 }
45 return t;
46 }).apply(this, arguments);Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
845 }
846 function D(e) {
847 let t = "";
848 for (let n in e) t += e[n]; 849 return t;
850 }
851 function P() {Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
24 function (s) {
25 for (var e, n, t = 1; t < arguments.length; t++) {
26 e = arguments[t];
27 for (n in e) 28 Object.prototype.hasOwnProperty.call(e, n) && (s[n] = e[n]); 29 }
30 return s;
31 },
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);
}