CSS-TricksCSS-Tricks

Test if dragenter/dragover Event Contains Files

Chris Coyier — Tue, 26 Mar 2013 00:20:28 +0000

HTML5 drag and drop is great for handling file uploads. But if that's the only thing you are using it for, it's nice to know if any particular dragenter or dragover event actually has files. Unlike, for example, just the dragging of some selected text.

Send the event object to this function and it will return the truth (assuming you are in a browser that supports all this):

function containsFiles(event) {

    if (event.dataTransfer.types) {
        for (var i = 0; i < event.dataTransfer.types.length; i++) {
            if (event.dataTransfer.types[i] == "Files") {
                return true;
            }
        }
    }
    
    return false;

}

Fix IE 10 on Windows Phone 8 Viewport

Chris Coyier — Sun, 27 Jan 2013 17:02:36 +0000

(function() {
  if (navigator.userAgent.match(/IEMobile\/10\.0/)) {
    var msViewportStyle = document.createElement("style");
    msViewportStyle.appendChild(
      document.createTextNode("@-ms-viewport{width:auto!important}")
    );
    document.getElementsByTagName("head")[0].appendChild(msViewportStyle);
  }
})();

Quick backstory

For IE 10 (desktop) to work in it's new "snap mode" you need to use this:

@-ms-viewport {
  width: device-width;
}

But that screws up some Windows Phone 8 phones, overriding the meta viewport tag and rendering as far too large on small screens. So the answer, for now, is this gnarly device detection/injection script.

Longer backstory

Matt Stow: Responsive Design in IE10 on Windows Phone 8
Tim Kadlec: Windows Phone 8 and Device-Width

Strip Whitespace From String

Chris Coyier — Sat, 05 Jan 2013 14:46:36 +0000

Whitespace, meaning tabs and spaces.

// Remove leading and trailing whitespace
// Requires jQuery
var str = " a b    c d e f g ";
var newStr = $.trim(str);
// "a b c d e f g"

// Remove leading and trailing whitespace
// JavaScript RegEx
var str = "   a b    c d e f g ";
var newStr = str.replace(/(^\s+|\s+$)/g,'');
// "a b c d e f g"

// Remove all whitespace
// JavaScript RegEx
var str = " a b    c d e   f g   ";
var newStr = str.replace(/\s+/g, '');
// "abcdefg"

Doesn't work with other types of whitespace though, for instance   (thin space) or (non-breaking space)

Lighten / Darken Color

Chris Coyier — Tue, 01 Jan 2013 14:45:54 +0000

The CSS preprocessors Sass and LESS can take any color and darken() or lighten() it by a specific value. But no such ability is built into JavaScript. This function takes colors in hex format (i.e. #F06D06, with or without hash) and lightens or darkens them with a value.

function LightenDarkenColor(col, amt) {
  
    var usePound = false;
  
    if (col[0] == "#") {
        col = col.slice(1);
        usePound = true;
    }
 
    var num = parseInt(col,16);
 
    var r = (num >> 16) + amt;
 
    if (r > 255) r = 255;
    else if  (r < 0) r = 0;
 
    var b = ((num >> 8) & 0x00FF) + amt;
 
    if (b > 255) b = 255;
    else if  (b < 0) b = 0;
 
    var g = (num & 0x0000FF) + amt;
 
    if (g > 255) g = 255;
    else if (g < 0) g = 0;
 
    return (usePound?"#":"") + (g | (b << 8) | (r << 16)).toString(16);
  
}

Usage

// Lighten
var NewColor = LightenDarkenColor("#F06D06", 20); 

// Darken
var NewColor = LightenDarkenColor("#F06D06", -20);

Demo

Inject New CSS Rules

Chris Coyier — Tue, 01 Jan 2013 14:35:29 +0000

If you need to change the style of an element with JavaScript, it's typically better to change a class name and have the CSS already on the page take effect and change the style. However, there are exceptions to every rule. For instance, you might want to programmatically change the a pseudo class (e.g. :hover). You can't do that through JavaScript for the same reason inline style="" attributes can't change pseudo classes.

You'll need to inject a new ' }).appendTo("body"); }

Usage

injectStyles('a:hover { color: red; }');

Demo

More Information

Style injection quirks in IE (Ryan Seddon).
Stack Overflow thread.