<script>
//Create a 16byte buffer
var buffer = new ArrayBuffer(16);
//Create a DataView referring to the buffer
var view1 = new DataView(buffer);
//Create a Int8Array view referring to the buffer
var view2 = new Int8Array(buffer);
//Put value of 32bits
view1.setInt32(0, 0x76543210);
//prints the 32bit value
document.write(view1.getInt32(0).toString(16) + "<br>");
//prints only 8bit value
document.write(view1.getInt8(0).toString(16) + "<br>");
document.write(view2[0].toString(16));
</script>
Internet Explorer is the only browser which really suffers from this in today's world. (Versions 5, 6, and 7 were dog slow. 8 does not show the same degradation.) What's more, IE gets slower and slower the longer your string is.
If you have long strings to concatenate then definitely use an array.join technique. (Or some StringBuffer wrapper around this, for readability.) But if your strings are short don't bother.