with the "onKeyPress" event handler I see that I can capture and examine the value of a keystroke before it is displayed on the screen. I have made good use of this for single character fields where I want to examine if the value is correct and also convert the value to upper case like so:
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<input
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type="text"
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name="f1"
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id ="f1"
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maxLength="1"
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onKeyPress="return isHorS(event);"
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/>
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function isHorS(evt)
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{
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evt = (evt) ? evt : event;
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var charCode = (evt.charCode) ? evt.charCode : ((evt.keyCode) ? evt.keyCode : ((evt.which) ? evt.which : 0));
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if (charCode != 8 && charCode != 9 && charCode != 32 && charCode != 72 && charCode != 104 && charCode != 83 && charCode != 115 )
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{
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alert("You must either leave blank or enter H or S!");
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document.getElementById("f1").value = "";
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}else{
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if (charCode == 104 || charCode == 115 )
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{
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var cUp = String.fromCharCode(charCode)
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document.getElementById("f1").value = cUp.toUpperCase();
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}
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}
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}
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As I said this works great when I am only dealing with one character. But for longer strings than one character, I would like to prevent unwanted characters from becoming part of the string. Can I use this technique by intercepting what the user is typing give them an alert and then cancel that keystroke entry?
