The usage of bind is to define a specified scope for called function. Because the key this is easy to refer another objet, experically window, instead of itself. Please pay attention to look at the following example:
1 //Global variables 2 window.name="Chromium"; 3 4 var person={ 5 name:"Pin" 6 } 7 8 function say() 9 { 10 alert("My name is "+this.name+"!"); 11 } 12 13 say(); //the result is : My name is Chromium! 14 15 var sayfunction=say.bind(person); 16 17 sayfunction(); //the result is : My name is Pin!
When the function say assign to a variable sayfunction, the scope of this function has been changed. However, if you use the function of bind to refer a specified object person, the scope will own the refer object person.