break

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

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 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');
}

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