Found unused expressions JS-0093
Bug risk
Minor
8 months ago
—
8 months old
Found unused expression
27 }
28
29 render() {
30 <div class={this.props.class_name}>{this.props.title}</div>;31 }
32}
33Found unused expression
3
4class Footer extends Component {
5 render() {
6 <> 7 <div class={this.props.class_name}> 8 {this.props.text} 9 </div>10 </>11 }
12}
13Found unused expression
7 }
8
9 render() {
10 <div onClick={() => this.handleClick.bind(this)} class={this.props.class_name}>{this.props.title}</div>;11 }
12}
13Found unused expression
7 }
8
9 render() {
10 <div onClick={() => this.handleClick.bind(this)} class={this.props.class_name}>11 Welcome to {this.props.title} TestingComponent Component12 </div>13 }
14}
15
Description
An unused expression that does not affect the state of the program indicates a logic error.
For example, if a programmer wants to increment the value of a variable a by one, and intends to do so through this code:
let a = 0
a = a + 1
console.log(a) // output 1
But because of a typo, writes the following:
let a = 0
a + 1
console.log(a)
Here, the expression a + 1 does nothing meaningful in the program's runtime.
The expression is thus considered "unused" and should be removed.
Bad Practice
0
if(0) 0
{0}
f(0), {}
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Recommended
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a