如何在Javascript中更新对象数组中每个对象的值？

Question

I have an array having multiple objects:

[ {col:1} {col:1} {col:1} {col:3} {col:3} {col:9} {col:12} {col:13} ]

I want to update this array such that col having values 1 will remain same while the next value (here 3) should become 2 and then next value(here 9) should become 3 and so on..

O/P:

[ {col:1} {col:1} {col:1} {col:2} {col:2} {col:3} {col:4} {col:5} ]

Please help.

Answer 1

Here is a fairly simple method:

 var arr = [ {col:1}, {col:1}, {col:1}, {col:3}, {col:3}, {col:9}, {col:12}, {col:13} ]; var current = 0; var prevEl = -1; for (var i = 0; i < arr.length; i++) { var el = arr[i].col; arr[i].col = el > prevEl ? ++current : current; prevEl = el; } console.log(arr); 

Answer 2

You can reduce your array:

var data = [
    { col: 1 }, { col: 1 },
    { col: 1 }, { col: 3 },
    { col: 3 }, { col: 9 },
    { col: 12 }, { col: 13 }
];

var result = data.reduce(function(r, i) {
    r.previous !== i.col && r.newValue++;
    r.previous = i.col;
    r.arr.push({ col: r.newValue });
    return r;
}, {arr: [], newValue: 0}).arr;

console.log(result);

I suppose your array is sorted by col , otherwise you need to sort it first.

Answer 3

Should do what is needed. Doesn't rely on any specific order in original array and assumes will always start at 1

 var data=[ {col:1} ,{col:1} ,{col:1} ,{col:3} ,{col:3}, {col:9} ,{col:12} ,{col:13} ]; var uniqueValues = data.reduce(function(a,c){ if(a.indexOf(c.col)===-1) { a.push(c.col); } return a; },[]).sort(function(a,b){ return ab; }); // produces [1,3,9,12,13] var res=data.map(function(item){ // use index of current col value from unique values .. plus one item.col=uniqueValues.indexOf(item.col) + 1; return item; }); document.getElementById('pre').innerHTML = JSON.stringify(res,null,4) 

 <pre id="pre"> 

Edit: if lowest col isn't 1 can still use uniqueValues.indexOf(item.col) + uniqueValues [0]

Answer 4

You could run a for loop to iterate through your array, and have if clauses to check for certain values; say the array object is called myArray :

var myArray = [ {col:1} {col:1} {col:1} {col:3} {col:3} {col:9} {col:12} {col:13} ];

for ( var i = 0; i < myArray.length; i++){
    if ( myArray[i] === 3 ){
        myArray[i] = 2;
    }
    // and so on.....
}