Node.JS / Javascript - 将字符串转换为整数，在我不期望它时返回NaN

Question

This is all in the context of a larger program, so Im going to try keep it simple, showing the offending lines only. I have an array of values that are numbers in string form a la "84", "32", etc.

Yet THIS line

console.log(unsolved.length + " " + unsolved[0] + " " + parseInt(unsolved[0]) + " " + parseInt("84"));

prints:

4 "84" NaN 84

"84" is the array element Im trying to parseInt! Yet it won't work unless I take it out of the context of an array and have it explicitly written. What's going on?

Answer 1

You can try removing the quotations from the string to be processed using this function:

function stripAlphaChars(source) { 
  var out = source.replace(/[^0-9]/g, ''); 

  return out; 
}

Also you should explicitly specify that you want to parse a base 10 number:

parseInt(unsolved[0], 10);

Answer 2

parseInt would take everything from the start of its argument that looks like a number, and disregard the rest. In your case, the argument you're calling it with starts with " , so nothing looks like a number, and it tries to cast an empty string, which is really not a number.

Answer 3

You should make sure that the array element is indeed a string which is possible to parse to a number. Your array element doesn't contain the value '84' , but actually the value '"84"' (a string containing a number encapsulated by ")

You'll want to remove the " from your array elements, possible like this:

function removeQuotationMarks(string) {
  return (typeof string === 'string') ? string.replace(/"|'/g, '') : string;
}

unsolved = unsolved.map(removeQuotationMarks);

Now all the array elements should be ready to be parsed with parseInt(unsolved[x], 10)

Answer 4

First we need to replace " to ' in give data using Regex and replace and then we need to cast.

 var i = 1; var j = "22" function stringToNumber(n) { return (typeof n === 'string') ? parseInt(Number(n.replace(/"|'/g, ''))) : n; } console.log(stringToNumber(i)); // 1 console.log(stringToNumber(j)); // 22