How does javascript determine whether a string is a number
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In javascript, you can use the Number () function and the isNaN () function to determine whether a string is a number, the syntax "isNaN (" string ", 10)"; if true is returned, the string is not a number, otherwise it is a number.
The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.
Javascript determines whether a string is a number
In the process of converting a string to a number through Number (), if the string contains a non-number, NaN will be returned, refer to the following code
Number ("Hello", 10); / / return NAN Number ("110,10); / / return 110Number (" t2110 ", 10); / / return NAN Number (" 1f10g ", 10); / / return NAN
So you can use isNaN () to determine whether the return value of Number () is NaN to determine whether the string is a number. If true is returned, the string is not a number, otherwise it is a number.
Implementation code:
Function f (a) {if (isNaN (Number (a Mag10) {console.log ("not a number");} else {console.log ("is a number");}}
Test:
F ("hello"); f ("10"); f ("d10jh6"); f ("10jh6")
Note: you cannot judge in the following ways:
Number ("Hello", 10) = = NaN;//return false Number ("110", 10) = = NaN;//return false
Because NaN and itself don't want to wait, this is special, and the way to judge NaN is to use isNaN ().
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