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How do I create a function that calls each provided function using JavaScript?
- PHPzforward
- 2023-08-24 12:41:021226browse
In JavaScript, functions are first-class objects, which means they can be passed as arguments to other functions. This is a powerful feature that can be used to create some interesting patterns.
One such pattern is the "invoke-each" pattern, where a function is created that calls each provided function with the arguments it receives.
Why use Invoke-Each mode?
There are several reasons why you might want to use the invoke-each pattern.
First, it can be used as a way to abstract away the details of how a set of functions are called. This is helpful if the function is called in a complex or repetitive way.
Second, it can be used to create some kind of "pipeline" where the output of each function is passed as input to the next function in the chain. This is a convenient way to string together a series of actions.
Finally, it can be used to create a "tee" function that calls multiple functions with the same parameters and collects the results. This is useful for logging, debugging, or other purposes.
How to implement the Invoke-Each pattern?
There are several different ways to implement calling each pattern.
The most straightforward approach is to simply loop through the provided functions and call each function with the arguments -
function invokeEach(functions, args) {
for (var i = 0; i < functions.length; i++) {
functions[i].apply(null, args);
}
}
In the above code, we loop through the functions and call each function using the Function.prototype.apply() method. This method allows us to call a function with a specific this value and parameter array.
We use the apply() method here because this is a convenient way to pass parameters as an array. You can also use the Function.prototype.call() method, which allows you to pass parameters as separate values.
Example
Below is a complete working code example.
<!doctype html>
<html>
<head>
<title>Examples</title>
</head>
<body>
<div id="result"></div>
<div id="result1"></div>
<div id="result2"></div>
<div id="result3"></div>
<script>
function foo(x) {
document.getElementById("result").innerHTML = 'foo: ' + x;
}
function bar(x) {
document.getElementById("result1").innerHTML = 'bar: ' + x;
}
function baz(x) {
document.getElementById("result2").innerHTML = 'baz: ' + x;
}
function qux(x) {
document.getElementById("result3").innerHTML ='qux: ' + x;
}
function invokeEach(functions, args) {
for (var i = 0; i < functions.length; i++) {
functions[i].apply(null, args);
}
}
invokeEach([foo, bar, baz, qux], [5]);
</script>
</body>
</html>
As you can see, the code example above defines four functions: foo(), bar(), baz(), and qux(). These functions simply print out a message using the provided parameters.
Next, we define the invokeEach() function, which accepts a function array and a parameter array. This function loops through the provided functions and calls each function with the provided arguments.
Finally, we call the invokeEach() function, passing in four functions and a single parameter 5. As expected, this results in every function being called with argument 5.
In this tutorial, we looked at the invoke-each pattern in JavaScript. This pattern can be used to create a function that calls each provided function with the arguments it receives.
We learned how to implement this pattern and some of the reasons why you might want to use it.
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