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while

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while , . .

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let n = 0;

while (n < 3) {
  n++;
}

console.log(n);
//  : 3

while (condition)
  statement

condition: . , statement . , while .
statement: . , .

, statement .

break statement , .
continue statement , condition .

while

while n 3 .

let n = 0;
let x = 0;

while (n < 3) {
  n++;
  x += n;
}

n x .

x n :

n = 1 x = 1
n = 2 x = 3
n = 3 x = 6

n < 3 , .

. , .

, , .

const iterator = document.createNodeIterator(document, NodeFilter.SHOW_COMMENT);
let currentNode;
while (currentNode = iterator.nextNode()) {
  console.log(currentNode.textContent.trim());
}

, .

while (currentNode = iterator.nextNode()) {

iterator.nextNode() , currentNode .
currentNode = iterator.nextNode() truthy.
console.log() .

... .

iterator.nextNode() null .
currentNode = iterator.nextNode() null, .
.

, === = . = === ( ).

, ESLint no-cond-assign , .

Expected a conditional expression and instead saw an assignment. ( )

. , .

const iterator = document.createNodeIterator(document, NodeFilter.SHOW_COMMENT);
let currentNode;
while ((currentNode = iterator.nextNode())) {
  console.log(currentNode.textContent.trim());
}

ESLint no-cond-assign Prettier , .

while ((currentNode = iterator.nextNode()) !== null) {

while ((currentNode = iterator.nextNode()) && currentNode) {

while .

const iterator = document.createNodeIterator(document, NodeFilter.SHOW_COMMENT);
for (
  let currentNode = iterator.nextNode();
  currentNode;
  currentNode = iterator.nextNode()
) {
  console.log(currentNode.textContent.trim());
}

. , .

Specification
ECMAScript 2027 LanguageSpecification # sec-while-statement

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