如何将参数传递给 JavaScript 函数中的匿名函数？

Question

Let's consider following example

function apple(fn) {
    fn();
}

apple(function(a) { // Here how do I pass an integer value for a ?
    console.log(a);
});

Answer 1

Arguments are passed to a function when it is called . So you can't per se. You have to pass them when you call it:

function apple(fn) {
    fn("Here you can pass an argument");
}

apple(function(a) {
    console.log(a);
});

If you want to define the value when you define the function, then just put it in the function:

function apple(fn) {
    fn();
}

apple(function() {
    console.log("Here you can hard code a value instead of using an argument");
});

A more complex solution would be to create a function which calls the anonymous function with arguments and then pass the new function… but that is just pointless complexity for the example you provide.

function apple(fn) {
    fn();
}

apple(function(a) {
    console.log(a);
}.bind(null, "Here you can pass an argument"));

Answer 2

Your code calls the anonymous function with no arguments:

function apple(fn) {
    fn(); //Here
}

You can pass something to it from apple :

function apple(fn) {
    fn(0);
}

apple(function(a) {
    console.log(a); //0
});

Or, you can let apple pass arguments for your anonymous function:

function apple(fn,...args) {
    fn(...args);
}

apple(function(a) {
    console.log(a); //0
}, 0);

Alternatively, you can bind your anonymous function, to prefix it with arguments:

function apple(fn) {
    fn();
}

apple((function(a) {
    console.log(a); //0
}).bind(undefined, 0));