Commonly used system functions in js are: 1. parseInt, extracts integers from a string; 2. parseFloat, extracts decimals from a string; isNaN, used to determine whether a variable is a number; 4. window.prompt is used to pop up a user input dialog box in the browser.
The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.
parseInt
parseFloat
isNaN
# is mainly used to determine whether a variable is a number.
window.prompt
[Recommended learning: javascript advanced tutorial]
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