break

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

break 陳述句會中斷目前的迭代、switch 或 label 陳述句，並將程式流程轉到被中斷之陳述句後的陳述句。

嘗試一下

let i = 0;

while (i < 6) {
  if (i === 3) {
    break;
  }
  i = i + 1;
}

console.log(i);
// Expected output: 3

語法

break [label];
label

可選的。欲中斷陳述句的標籤 (label) 識別。若不是要中斷迭代或 switch，則需加此參數。

說明

中斷陳述 break 可加上標籤 (label) 參數，使其跳出被標籤的陳述語句。此中斷陳述 break 必須被包含在被標籤的陳述語句中。被標籤的陳述語句可被添加於任一個區塊 (block) 前，而非限定在迴圈陳述。

範例

下面函式包含一個中斷陳述 break ，當 i 值為 3 時，中斷 while 迴圈，並回傳 3 * x 。

js
function testBreak(x) {
  var i = 0;

  while (i < 6) {
    if (i == 3) {
      break;
    }
    i += 1;
  }

  return i * x;
}

The following code uses break statements with labeled blocks. A break statement must be nested within any label it references. Notice that inner_block is nested within outer_block.

js
outer_block: {
  inner_block: {
    console.log("1");
    break outer_block; // breaks out of both inner_block and outer_block
    console.log(":-("); // skipped
  }
  console.log("2"); // skipped
}

The following code also uses break statements with labeled blocks but generates a Syntax Error because its break statement is within block_1 but references block_2. A break statement must always be nested within any label it references.

js
block_1: {
  console.log('1');
  break block_2; // SyntaxError: label not found
}

block_2: {
  console.log('2');
}

規範

Specification
ECMAScript® 2026 Language Specification
# sec-break-statement

瀏覽器相容性

參見