Prefer that
for-in loops should include an if statement JS-0051
Anti-pattern
Minor
9 months ago
—
a year old
Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
1227 WordCloud.minFontSize = minFontSize
1228 WordCloud.stop = function stop () {
1229 if (timer) {
1230 for (var timerId in timer) {1231 window.clearImmediate(timer[timerId])1232 }1233 }
1234 }
1235Wrap the body of a for-in loop in an if statement with a hasOwnProperty guard
846 span.style[cssProp] = styleRules[cssProp]
847 }
848 if (attributes) {
849 for (var attribute in attributes) { 850 span.setAttribute(attribute, attributes[attribute]) 851 } 852 }
853 if (classes) {
854 span.className += classesWrap the body of a for-in loop in an if statement with a hasOwnProperty guard
842 styleRules.color = color
843 }
844 span.textContent = word
845 for (var cssProp in styleRules) { 846 span.style[cssProp] = styleRules[cssProp] 847 } 848 if (attributes) {
849 for (var attribute in attributes) {
850 span.setAttribute(attribute, attributes[attribute])
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);
}