function runOnce(fn, context) { //控制讓函數只觸發(fā)一次
  return function () {
    try {
      fn.apply(context || this, arguments);
    }
    catch (e) {
      console.error(e);//一般可以注釋掉這行
    }
    finally {
      fn = null;
    }
  }
}
 
// Usage 1:
var a = 0;
var canOnlyFireOnce = runOnce(function () {
  a++;
  console.log(a);
});
 
canOnlyFireOnce(); //1
canOnlyFireOnce(); // nothing
canOnlyFireOnce(); // nothing
 
// Usage 2:
var name = "張三";
var canOnlyFireOnce = runOnce(function () {
  console.log("你好" + this.name);
});
canOnlyFireOnce(); //你好張三
canOnlyFireOnce(); // nothing
 
// Usage 3:
var obj = {name: "天涯孤雁", age: 24};
var canOnlyFireOnce = runOnce(function () {
  console.log("你好" + this.name);
}, obj);
canOnlyFireOnce(); //你好天涯孤雁
canOnlyFireOnce(); // nothing

因為返回函數執(zhí)行一次后，fn = null將其設置未null，所以后面就不會執(zhí)行了。再貼一個網上別人分享的代碼，道理一樣的：

function once(fn, context) { 
  var result;
 
  return function() { 
    if(fn) {
      result = fn.apply(context || this, arguments);
      fn = null;
    }
 
    return result;
  };
}
 
// Usage
var canOnlyFireOnce = once(function() {
  console.log('Fired!');
});
 
canOnlyFireOnce(); // "Fired!"
canOnlyFireOnce(); // nothing

以上就是為大家整理讓javascript只執(zhí)行一次的函數示例，有需要的可以參考。

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