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I wonder why, as soon as the page loads, the function btw_bijtellen () is called. I wanted to call it by clicking...

var $ = function (id) {
    return document.getElementById (id);
}

function btw_bijtellen () {
    window.alert("we want to calculate something after clicking th button");
}

$("bereken").onclick = btw_bijtellen ();

You've added () which causes the function to execute.

For example:

var myFunc1 = function() {
    alert('Hello');
}(); // <--- () causes self execution

var myFunc2 = function() {
    return 5 + 5;
};

var some_value = myFunc2(); // <--- Again () causes execution (you'd expect this one)

In your case, as mentioned in comments you're basically telling the onclick to set its value to the return value of the function.

If you drop the () it should run as expected.

Why is this javascript function running without being called?, Change your SetupButtonClicks function: $('#btnJavaPHP').click(DoHPStuff);. The way you've got it coded, you're telling Javascript to call the  The problem is that a function calls on the next object from Parse.com which shows its details but, for some reason, it executes the function twice or even 3 times, skipping 1 or 2 objects that have to be shown.

If you want the function to be called on click then use

$("bereken").on('click', btw_bijtellen);
Update (As per query from WAO)

If you need to pass the argument, then you need to specify as the second argument. the $.on() gets the data in the event handler

$("bereken").on('click', {key1: value1, key2: value2, keyn: valuen}, btw_bijtellen);

where, you can get your parameters from event.data

var function = btw_bijtellen(event) {
    var data = event.data;
    console.log(data);

    var key1 = event.data.key1;
    console.log(key1);  // this will output value1
}

Have a read on this link jQuery $.on() api

JavaScript Function Invocation, In this tutorial, we will use invoke, because a JavaScript function can be invoked without being called. Invoking a Function as a Function. Example. function  The function when called the first time will do the init. It will then immediately overwrite itself to return false the next time its called. The second time the function is called, the function body will only contain return false.

Putting () after a function name is how you call it.

If you want to assign the btw_bijtellen to onclick then remove the () from the last line of the code in the question.

With the () there, you are calling the function and assigning its return value to onclick. Since that function has no return statement, that value will be undefined which is not what you want.

[Solved] Why javascript function called automatically on page load , Sumit Kumar Singh India wrote: When i put in body then only this happened. When i put this javascript code in head then its not called  Putting after a function name is how you call it.. If you want to assign the btw_bijtellen to onclick then remove the from the last line of the code in the question.. With the there, you are calling the function and assigning its return value to onclick.

Why does Javascript function run without being called?? Solutions , Find answers to Why does Javascript function run without being called?? from the expert community at Experts Exchange. Because you are calling that function instead of passing the function to onClick, change that line to this: <button type="submit" onClick={() => { this.props.removeTaskFunction(todo) }}>Submit</button> => called Arrow Function, which was introduced in ES6, and will be supported on React 0.13.3 or upper.

Javascript Self Invoking Functions, You must be aware of the fact that javascript functions run immediately However, you can make the function auto-run by making it self-executing function like this: Above, doStuff function will get called every 10 seconds. The code inside a function is executed when the function is invoked. It is common to use the term "call a function" instead of "invoke a function". It is also common to say "call upon a function", "start a function", or "execute a function". In this tutorial, we will use invoke, because a JavaScript function can be invoked without being called.

4 ways to call a function in JavaScript, Functions in JavaScript can be called in different ways. Now, without further ado, let's introduce the four ways in which a function can be called. That being the case, this is a more specialized case of how to call a function. Functions are one of the fundamental building blocks in JavaScript. A function is a JavaScript procedure—a set of statements that performs a task or calculates a value. To use a function, you must define it somewhere in the scope from which you wish to call it.

Comments
  • By the way, for @bert, this means your onclick handler is assigned "undefined" - because running this function which returns "undefined" assigns this result to onclick.
  • @Lloyd So only parenthesis when declaring or calling, all the rest (which leafs only assigning?) without parenthesis?
  • Declaring or calling yes. For assignment just drop them.
  • what if you want to pass an argument to 'btw_bijtellen' function?