Assignment operators should not be used in return statements JS-0086
Anti-pattern
Minor
3 months ago
—
a year old
Arrow function should not return assignment
1142
1143 setRenderAnimation(value) {
1144 this.renderAnimation = value;
1145 this.renderInstances.forEach((r) => r.renderAnimation = this.renderAnimation);1146 }
1147
1148
Description
One of the interesting, and sometimes confusing, aspects of JavaScript is that assignment can happen at almost any point. Because of this, an errant equals sign can end up causing assignment when the true intent was to do a comparison. This is especially true when using a return statement. For example:
function doSomething() {
return foo = bar + 2;
}
It is difficult to tell the intent of the return statement here.
It's possible that the function is meant to return the result of bar + 2, but then why is it assigning to foo?
It's also possible that the intent was to use a comparison operator such as == and that this code is an error.
Because of this ambiguity, it's considered a best practice to not use assignment in return statements.
Bad Practice
function doSomething() {
return foo = bar + 2;
}
function doSomething() {
return foo += 2;
}
Recommended
function doSomething() {
return foo == bar + 2;
}
function doSomething() {
return foo === bar + 2;
}
function doSomething() {
return (foo = bar + 2);
}