Discord GitHub GitHub Twitter

Lint Rules

noConstantCondition (since v12.1.0)

Disallow constant expressions in conditions

Examples

Invalid

if (false) {
    doSomethingUnfinished();
}
nursery/noConstantCondition.js:1:5 lint/nursery/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected constant condition.
  
  > 1 │ if (false) {
      │     ^^^^^
    2 │     doSomethingUnfinished();
    3 │ }
  

if (Boolean(1)) {
    doSomethingAlways();
}
nursery/noConstantCondition.js:1:5 lint/nursery/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected constant condition.
  
  > 1 │ if (Boolean(1)) {
      │     ^^^^^^^^^^
    2 │     doSomethingAlways();
    3 │ }
  

if (undefined) {
    doSomethingUnfinished();
}
nursery/noConstantCondition.js:1:5 lint/nursery/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected constant condition.
  
  > 1 │ if (undefined) {
      │     ^^^^^^^^^
    2 │     doSomethingUnfinished();
    3 │ }
  

for (;-2;) {
    doSomethingForever();
}
nursery/noConstantCondition.js:1:7 lint/nursery/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected constant condition.
  
  > 1 │ for (;-2;) {
      │       ^^
    2 │     doSomethingForever();
    3 │ }
  

while (typeof x) {
    doSomethingForever();
}
nursery/noConstantCondition.js:1:8 lint/nursery/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected constant condition.
  
  > 1 │ while (typeof x) {
      │        ^^^^^^^^
    2 │     doSomethingForever();
    3 │ }
  

var result = 0 ? a : b;
nursery/noConstantCondition.js:1:14 lint/nursery/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected constant condition.
  
  > 1 │ var result = 0 ? a : b;
      │              ^
    2 │

Valid

if (x === 0) {
    doSomething();
}

for (;;) {
    doSomethingForever();
}

while (typeof x === "undefined") {
    doSomething();
}

do {
    doSomething();
} while (x);

var result = x !== 0 ? a : b;