Software development and programming - Showing posts from 2025

Showing posts from 2025

The approach you take when creating a "class"

What style do you use for creating a "class"? There are a few ways to get class-like behavior in javascript, the most common seem to be prototype based like this: function Vector(x, y, x) { this.x = x; this.y = y; this.z = z; return this; } Vector.prototype.length = function () { return Math.sqrt(this.x * this.x ... ); } and closure based approaches similar to function Vector(x, y, z) { this.length = function() { return Math.sqrt(x * x + ...); } } For various reasons the latter is faster, but I've seen (and I frequently do write) the prototype version and was curious as to what other people do. My tests have shown that the closure based approach is slower. You have to instantiate a separate closure for each object. The prototype approach shares the methods with all instances. 7 Answers Assigning functions to the prototype is better (for public methods) because all instances of the class will share the same copy of the method. If you assign t...

How can I enable disabled radio buttons? The following code works great in IE, but not in FF or Safari. I can't for the life of me work out why. The code is supposed to disable radio buttons if you select the "Disable 2 radio buttons" option. It should enable the radio buttons if you select the "Enable both radio buttons" option. These both work... However, if you don't use your mouse to move between the 2 options ("Enable..." and "Disable...") then the radio buttons do not appear to be disabled or enabled correctly, until you click anywhere else on the page (not on the radio buttons themselves). If anyone has time/is curious/feeling helpful, please paste the code below into an html page and load it up in a browser. It works great in IE, but the problem manifests itself in FF (3 in my case) and Safari, all on Windows XP. function SetLocationOptions() { var frmTemp = document.frm; var selTemp = frmTemp.user; if (selTemp.selecte...

What's the difference in closure style There are two popular closure styles in javascript. The first I call anonymous constructor : new function() { var code... } and the inline executed function : (function() { var code... })(); are there differences in behaviour between those two? Is one "better" over the other? 5 Answers Both cases will execute the function, the only real difference is what the return value of the expression may be, and what the value of "this" will be inside the function. Basically behaviour of new expression Is effectively equivalent to var tempObject = {}; var result = expression.call(tempObject); if (result is not an object) result = tempObject; Although of course tempObject and result are transient values you can never see (they're implementation details in the interpreter), and there is no JS mechanism to do the "is not an object" check. Broadly speaking the "new function() { .. }" meth...

Getting the text from a drop-down box

Getting the text from a drop-down box This gets the value of whatever is selected in my dropdown menu. document.getElementById('newSkill').value I cannot however find out what property to go after for the text that's currently displayed by the drop down menu. I tried "text" but that didn't have the answer, does anybody here know? For those not sure, here's the HTML for a drop down box. <select name="newSkill" id="newSkill"> <option value="1">A skill</option> <option value="2">Another skill</option> <option value="3">Yet another skill</option> </select> 14 Answers Based on your example HTML code, here's one way to get the displayed text of the currently selected option: var skillsSelect = document.getElementById("newSkill"); var selectedText = skillsSelect.options[skillsSelect.selectedIndex].text; For those late to the party,...