Alert object type when JavaScript numeric size comparison

Use JS to get the value of the two-digit input box on the page and compare it to size. The result may be confusing to you, such as code:

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var v1 = $ (' #input1 '). Val (); var v2 = $ (' #input2 '). Val (); Alert (V1 > V2);

If you enter 2 in the INPUT1 input 10,input2. 10 is definitely greater than 2, so the alert box above should pop true, but it actually gives false. Why? The corresponding number 10 greater than 2 is no doubt, if it is a string comparison, then the result is just the opposite. The type that is worth getting from the page above is string.

Cases

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<script> Alert (' > ' 40 '); False because the 1<4 Alert (> 40.00); True </script>

In a JS script, you sometimes need to compare the size of two values, and both of these values are numbers,

Such as

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function Getbigger (A, b) { Return a > B? A:B; }

If you explicitly want to make a numeric comparison, you need to display the conversion to numbers, such as using parseint, parsefloat, and another method is to use the subtraction operator, such as: v1–v2 > 0, when JS in the operation before the type conversion.

Cases

code is as follows	copy code
<script language= "javascript" Function compare () ... { if (parseint (Document.form1.a.value) < parseint (Document.form1.b.value)) ... { Alert ("a <b"); }else ... { Alert ("A>b"); } } </script> <form name=form1> <input name=a type=text/> <input name=b type=text/> <input type=button onclick= "compare ()" value= "compare"/> </form

parseint (cString) An integer that is converted from a string cString a non-empty character and stops when the decimal point or other 0-9 characters are encountered, such as " -1234a", "1234.0", which returns 1234; if a 0-9 character except the first symbol is not, Will return nan, such as "-a", "abc", and so on;

In addition, because the addition operator supports numbers and strings at the same time, be careful when using this time. For example A + B, if one is a string type and one is a numeric type, the other is converted to a string type before performing the operation, so it is actually a string linking operation rather than the desired arithmetic operation. In the case of determining whether an arithmetic operation is to be performed, for an unknown type of argument, in the case of insurance, use parseint for type conversion.