James Fishwick

You need to convert a string to a number.  Several ways, with varying purposefulness:

Number constructor called as a function simply performs type conversion:

// type conversion
Number("911");        // 911
Number("20px");       // NaN
Number("2e1");        // 20, exponential notation
Number("010");        // 10 (The Number constructor doesn't detect octals)
Number("8,569")       // Nan
Number(8,569)         // 8
Number("8.569")       // 8.569
Number("0xF");        // 15 (But it can handle numbers in hexadecimal notation)
Number("false");      // NaN
Number(true)          // 1

parseInt() performs parsing into an integer*:

// parsing:
parseInt("999");        // 999
parseInt("20px");       // 20 (will stop parsing and drop any part of the string it can't figure out)
parseInt("fi5e")        // NaN (string has to start making some sense right away)
parseInt("10100", 2);   // 20
parseInt("2e1");        // 2
parseInt("010");        // 8 (if parseInt detects a leading zero on the string, it will parse the number in octal base)
parseInt("010", 10);    // 10 (decimal radix used)
parseInt("0xF");        // 15 (can also handle numbers in hexadecimal notation
parseInt("22.5")        // 22 (because the decimal point is an invalid character for an integer)
Number("false");        // NaN
Number(true)            // NaN

*It’s always a good idea to supply a radix to parseInt(value, radix) that way you don’t have accidental octal mode conversions.

The parseFloat() method works in a similar way to parseInt() however the string must represent a floating-point number in decimal form, not octal or hexadecimal.

parseFloat("1234blue"); 	// 1234.0
parseFloat("0xA"); 	// NaN
parseFloat("22.5"); 	// 22.5
parseFloat("22.34.5"); 	// 22.34
parseFloat("0908"); 	// 908
parseFloat("James1980"); 	// NaN

The Unary Plus method (+num) is basically a short cut for casting to a number via Number(). Just a nice shortcut really.

+"911"; // 911
+"20px";       // NaN
//etc etc
num = 1 + +"2"; // num is assigned the value 3
+true; // 1 (just saying...)

Finally, you can attempt some simple math on your string, does the same as the above.

"123" / 1; // 123
"123.987" * 1; // 123.987

You can use num / 1;, num * 1;, 0 + num; or 1 * num;.

If you’re interested in a speed comparison, see this test case (this would only matter for huge numbers of conversions. HUGE.)

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