btctocn

1. It is suggested that you first assign the background value to a text box or an element, and then JS gets the value before judging.

2.

I don't understand. Do you want to get the text of a JS formula and return the result

for example:

< pre t = "code" L = "JS" > $(& quot# id"). innerHTML=" 1+2-3*4/5";

to get text results, you can use eval():

< pre t = "code" L = "JS" > alert (EVAL ($(& quot# id"). innerHTML));// 0.6000000000000001