Find max from array of char and number

Question

I have an array like ['VS', 'V1', 'V2', 'V3', 'VE']

I am using substring to get second part which returns me 'S', '1', '2', '3', 'E'

I have to find the max integer value which will be 3 in this case. I tried this solution but I am geting NaN.

Any suggestion?

• starcorn: You need to filter out the none numeric characters first

Answer 1

You could check the casted value for truthyness and use a zero as default value.

+s[1] || 0
 s[1] take the character at index 1
+ use unary plus for converting string to number, this could return NaN
 || 0 in this case take zero instead of the falsey value, like NaN

var array = ['VS', 'V1', 'V2', 'V3', 'VE'],
 max = Math.max(...array.map(s => +s[1] || 0));
console.log(max);

ES5

var array = ['VS', 'V1', 'V2', 'V3', 'VE'],
 max = Math.max.apply(null, array.map(function (s) { return +s[1] || 0; }));
console.log(max);

• αƞjiβ: what +s[1] doing here? can you please explain.
• starcorn: I would use something like parseInt() instead. To make the code more readable
• Michał Dąbrowski: @αƞjiβ the + forces the result to be a number, s[1] is second element of string (a string is an array of characters).

Answer 2

The issue is that the values are still strings after you get rid of the first char.

var ary = ['VS', 'V1', 'V2', 'V3', 'VE'];
var ary2 = ary.map(function(val){
 // Get the second character and convert to a number if possible
 // ruturn that number or null
 return parseInt(val.charAt(1)) || null;
});
// Now, the function will work
Array.max = function( array ){
 return Math.max.apply( Math, array );
};
console.log(Array.max(ary2));

Answer 3

You may want to remove any non-numbers. This should return an array containing only numbers of your array.

['S','1','2','3','E'].filter((item) => parseInt(item)).map((item) => parseInt(item))

will return:

 [1, 2, 3]