break

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。

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。

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 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.

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.

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

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

• continue
• label
• switch