js for loop and exit

js for loop and exit

1. for loop

continue: 跳出本地循环，进入下一次循环

for(let i = 0; i < 5; i++) {
    
    
    if(i == 3) {
    
    
        continue;
    }
    console.log(i); // 0，1，2，4
}

break：跳出当前循环(如为多层循环，不影响外层循环)

for(let i = 0; i < 5; i++) {
    
    
    if(i == 3) {
    
    
        break;
    }
    console.log(i);  // 0,1,2
}

return：结束当前函数调用

以上所说同样适用于for循环对象。

let obj = {
    
    
  name: 'Anny',
  age: 14,
  address: '宁波市'
}

for (let key in obj) {
    
    
  if (key === 'age') {
    
    
    continue // 当key等于age时，就会跳过此次循环，进入下一次循环
  }
  console.log(key) // name address
}

for (let key in obj) {
    
    
  if (key === 'age') {
    
    
    break // 当key等于age时，就会跳过此次循环，进入下一次循环
  }
  console.log(key) // name 
}

2. forEach loop

Under normal circumstances, this cycle cannot be ended, but it can be terminated with try catch;

let arr1 = [1, 3, 5, 7, 9]
try {
    
    
    // 执行到第3次，结束循环
    arr1.forEach(function(item,index){
    
    
        if (item == 7) {
    
    
            throw new Error("End");
        }
        console.log(item); // 1,3,5
    });
} catch(e) {
    
    
    if(e.message!="End") throw e;
}