Instantly summing up two numbers with javascript

Question

Instantly summing up two numbers with javascript

In my web development work using Visual Studio 2008, I encountered an interesting challenge. On a webpage, I have three textboxes labeled "Price," "Quantity," and "Amount." The task at hand is to calculate the value of "Amount" by multiplying the values entered into "Price" and "Quantity." The catch is, I want this calculation to occur automatically without requiring the user to click on any buttons. The desired sequence is for the user to input a value in the "Price" textbox, followed by a value in the "Quantity" textbox. Upon exiting the "Quantity" textbox, I expect the product to appear in the "Amount" textbox instantaneously, all done through JavaScript.

javascript visual-studio-2010

Answer 1

Answer №1

It seems like you're referring to the blur event, which is triggered when a text input loses focus (such as clicking outside of it).

To attach this event to your textarea, use the following code:

price.addEventListener("blur", function( event )
{
    // perform actions here
}, true);

Here's a JSFiddle demonstration: http://jsfiddle.net/egLzz5gb/

Answer 2

It seems like you're referring to the blur event, which is triggered when a text input loses focus (such as clicking outside of it).

To attach this event to your textarea, use the following code:

price.addEventListener("blur", function( event )
{
    // perform actions here
}, true);

Here's a JSFiddle demonstration: http://jsfiddle.net/egLzz5gb/

Answer 3

Answer №2

To detect changes in the input fields, you can utilize the change event. This event triggers whenever there is a modification in the input value. Although the structure of your form may vary, the following code snippet illustrates a basic approach:

quantityInput.addEventListener('change', function(){
  amountInput.value = parseInt(quantityInput.value) * parseInt(priceInput.value);
});

If you are dealing with decimal numbers, consider using parseFloat() instead of parseInt(). It's important to exercise caution, and for accurate results, it's advisable to incorporate Math.round() due to precision issues with floating-point calculations.

Answer 4

To detect changes in the input fields, you can utilize the change event. This event triggers whenever there is a modification in the input value. Although the structure of your form may vary, the following code snippet illustrates a basic approach:

quantityInput.addEventListener('change', function(){
  amountInput.value = parseInt(quantityInput.value) * parseInt(priceInput.value);
});

If you are dealing with decimal numbers, consider using parseFloat() instead of parseInt(). It's important to exercise caution, and for accurate results, it's advisable to incorporate Math.round() due to precision issues with floating-point calculations.

Answer 5

Answer №3

Cost: <input type="text" id="cost">
Quantity: <input type="text" id="quantity" onkeyup="displayTotal()">
Total: <input type="text" id="total">

<script>
function displayTotal() {
    var c = document.getElementById("cost");
    var q = document.getElementById("quantity");
    var t = document.getElementById("total");
    t.value = c.value * q.value ;
}

Answer 6

Cost: <input type="text" id="cost">
Quantity: <input type="text" id="quantity" onkeyup="displayTotal()">
Total: <input type="text" id="total">

<script>
function displayTotal() {
    var c = document.getElementById("cost");
    var q = document.getElementById("quantity");
    var t = document.getElementById("total");
    t.value = c.value * q.value ;
}

Instantly summing up two numbers with javascript

Answer №1

Answer №2

Answer №3

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