Converting Values

The possibilities are endless for the types of values that can be converted from one form to another. Script 17.11 shows just one example: how to convert kilometers to miles.

Script 17.11. You can create bookmarklets for almost any kind of unit conversion. This script converts kilometers to miles.

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  javascript:var expr=prompt('Length in kilometers:','');if(isNaN(parseFloat(expr))) {alert(  expr+' is not a number')}else {alert('Length in miles is '+Math.round (expr*6214)/10000);}  

To convert kilometers to miles:

1.	javascript:var expr=prompt('Length in kilometers:',''); The bookmarklet starts by prompting the user for a length in kilometers ( Figure 17.20 ). Figure 17.20. First, ask for the number to be converted.
2.	if(isNaN(parseFloat(expr))) Check to see if the user entered a numeric value.
3.	{alert(expr+' is not a number')} If not, put up an error message.
4.	else{alert('Length in miles is '+Math.round(expr*6214)/10000);} Otherwise, convert the value to miles and display it as an alert, as shown in Figure 17.21 . Figure 17.21. JavaScript returns the result of the conversion.

Tips

• It's a straightforward process to adapt this script into any kind of conversion you need. Just change the label in step 1, and replace the math expression in step 4 to the correct expression for the particular conversion you're looking for.

• You can make up a bunch of book- marklets with different conversions and then organize them all into folders in your Bookmarks or Favorites menu. Conversions can be just a mouse click away.