您必须先将字符串解析为数字，然后才能将其相乘:

You have to parse string as a number before you can multiply it:

str = str.replace(/[0-9]+(?:\.[0-9]*)?/g, function(m) { return 2*parseFloat(m)+''; });

您不能在javascript中将字符串相乘！

You cannot multiply strings in javascript !

"" * 2 // NaN