将字符串转换为数字 node.js

You do not have to install something.

parseInt(req.params.year, 10);

should work properly.

console.log(typeof parseInt(req.params.year)); // returns 'number'

What is your output, if you use parseInt? is it still a string?

Using parseInt() is a bad idea mainly because it never fails. Also because some results can be unexpected, like in the case of INFINITY.
Below is the function for handling unexpected behaviour.

function cleanInt(x) {
x = Number(x);
return x >= 0 ? Math.floor(x) : Math.ceil(x);
}

See results of below test cases.

console.log("CleanInt: ", cleanInt('xyz'), " ParseInt: ", parseInt('xyz'));
console.log("CleanInt: ", cleanInt('123abc'), " ParseInt: ", parseInt('123abc'));
console.log("CleanInt: ", cleanInt('234'), " ParseInt: ", parseInt('234'));
console.log("CleanInt: ", cleanInt('-679'), " ParseInt: ", parseInt('-679'));
console.log("CleanInt: ", cleanInt('897.0998'), " ParseInt: ", parseInt('897.0998'));
console.log("CleanInt: ", cleanInt('Infinity'), " ParseInt: ", parseInt('Infinity'));

result:

CleanInt:  NaN  ParseInt:  NaN
CleanInt:  NaN  ParseInt:  123
CleanInt:  234  ParseInt:  234
CleanInt:  -679  ParseInt:  -679
CleanInt:  897  ParseInt:  897
CleanInt:  Infinity  ParseInt:  NaN

Not a full answer Ok so this is just to supplement the information about parseInt, which is still very valid. Express doesn't allow the req or res objects to be modified at all (immutable). So if you want to modify/use this data effectively, you must copy it to another variable (var year = req.params.year).

You can parse string to number in several ways.

-Number()

-parseInt()

-parseFloat()

Example:

Number("256.123") //returns 256.123

Number("252px") //returns NaN

parseInt("256.123") //returns 256

parseInt("256px") //returns 256

parseFloat("256") //returns 256

parseFloat("256.123") //returns 256.123

parseFloat("256.23px") //returns 256.23