Compare numeric values in javascript array

Question

I have an array like below

var nums = ["1", "2", "2", "3", "4", "4", "5"];

Here I am trying to compare the values in array and test whether the values are in ascending order or not.

If two array values are same, I need to skip that. If order is like 1,3,2.. then I will throw an error that they are in wrong order. I want to use pure javascript here.

What did you try so far and what issues have you encountered? — Jozef Legény, Mar 26 '15 at 18:20
And what is your specific problem? Do you know how to iterate over an array? How to compare two values? How to convert a string to a number? — Felix Kling, Mar 26 '15 at 18:26
is it possible to check this for var dates = ["mar 1", "mar 2", "mar 2", "mar 3", "mar 4", "mar 4", "mar 5"]; ? — Vamshi, Mar 27 '15 at 13:20

juvian · Answer 1 · 2015-03-26T18:29:21.003

1

Seems easy:

function isAscending(arr){
    asc = true;
    for(var i=1;i<arr.length;i++){
        if(Number(arr[i]) < Number(arr[i-1])){
            asc = false;
            break;
        }
    }
    return asc
}

edited Mar 26 '15 at 18:29

answered Mar 26 '15 at 18:21

juvian

15,875
2
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@halex didn't notice it was strings, fixed – juvian Mar 26 '15 at 18:25
`Number` would be more appropriate than `parseFloat`. – Felix Kling Mar 26 '15 at 18:26
@FelixKling not a big difference, but changed (http://stackoverflow.com/questions/11988547/what-is-the-difference-between-number-and-parsefloat) – juvian Mar 26 '15 at 18:29

Yaar Hever · Answer 2 · 2015-03-26T19:18:38.080

1

I would loop through each pair of items using parseInt() to get the numeric value out of the strings and after the loop, compare the value of the incremented index to the number of pairs.

EDIT: As suggested by Rick Hitchcock, instead of breaking from the loop, we can just return false if any pair is not ascending or equal and true if the whole loop went through.

function isAscending(array) {
    for (var i = 0; i < (array.length - 1); i++) {
        if (parseInt(array[i]) > parseInt(array[i+1])) {
            return false;
        }
    }
    return true;
}

edited Mar 26 '15 at 19:18

answered Mar 26 '15 at 18:44

Yaar Hever

81
1
6

1

You could replace `break` with `return false`, and replace `return (i == nPairs)` with `return true`. – Rick Hitchcock Mar 26 '15 at 19:11

FarazShuja · Answer 3 · 2015-03-26T19:11:10.210

1

Using jquery

var num = [1,5,3,3,4,4];
var sortedNum = num.slice(0).sort(function(a,b) {
    return a-b;
});
//if its sorted
if(num.join(',') === sortedNum.join(',')) {
    //get only unique elems
    var finalArr = $.grep(num, function(el, index) {
        return index === $.inArray(el, num);
    });
    console.log(finalArr);
}
else {
    console.log('Error Not Sorted');
}

edited Mar 26 '15 at 19:11

answered Mar 26 '15 at 18:52

FarazShuja

2,287
2
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Compare numeric values in javascript array

3 Answers3