解释
A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.
callback() function 是作为argument传到另一个函数的函数。
实例
function greeting(name) {
alert('Hello ' + name);
}
function processUserInput(callback) {
var name = prompt('Please enter your name.');
callback(name);
}
processUserInput(greeting);
等价于
function greeting(name) {
alert('Hello ' + name);
}
function processUserInput() {
var name = prompt('Please enter your name.');
greeting(name);
}
processUserInput();
分析
processUserInput(greeting);
传进去greeting(greeting 在函数内部就用callback表示了),先执行输入name,然后执行greeting。如果我想再实现processUserInputfareWell()
函数,我只需要传processUserInput(fareWell);
第二种方法的话先然就不能改了,如果我想再加一个fareWell()
函数,就只能重新写一个新的函数processUserInput2()