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noConstantCondition (since v1.0.0)

Diagnostic Category: lint/correctness/noConstantCondition

Sources:

Disallow constant expressions in conditions

Examples

Section titled Examples

Invalid

Section titled Invalid
if (false) {
    doSomethingUnfinished();
}
correctness/noConstantCondition.js:1:5 lint/correctness/noConstantCondition ━━━━━━━━━━━━━━━━━━━━━━━━

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

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

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

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

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

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

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

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

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

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

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

Valid

Section titled Valid
if (x === 0) {
    doSomething();
}


for (;;) {
    doSomethingForever();
}


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


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


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


// Exception
while (true) {
    if (x) { break; }
    x = f();
}
Section titled Related links