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 。

function testBreak(x) {  var i = 0;  while (i < 6) {    if (i == 3) {      break;    }    i += 1;  }  return i * x;}

The following code usesbreak statements with labeled blocks. Abreak statement must be nested within any label it references. Notice thatinner_block is nested withinouter_block.

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 usesbreak statements with labeled blocks but generates a Syntax Error because itsbreak statement is withinblock_1 but referencesblock_2. Abreak statement must always be nested within any label it references.

block_1: {  console.log('1');  break block_2; // SyntaxError: label not found}block_2: {  console.log('2');}

規範

瀏覽器相容性

參見

• continue
• label
• switch