How to select an element from a JavaScript array when I only know the value for one of the properties of the element?

Question

I have the following JavaScript object:

{
    "DPI": "66.8213457076566",
    "width": "563.341067",
    "editable": "True",
    "pricecat": "6",
    "numpages": "2",
    "height": "400",
    "page": [{
        "filename": "999_9_1.jpg",
        "line": [{
            "test": "test 1",
            lineid: 22
        },
        {
            "test": "test 2",
            lineid: 22
        },
        {
            "test": "test 3",
            lineid: 22
        },
        {
            "test": "test 4",
            lineid: 22
        },
        {
            "test": "blank",
            lineid: 22
        }]
    },
    {
        "filename": "999_9_2.jpg",
        "line": []
    }]
}

I can do most things with strings like measurements.page[0].line[0].lineid;

But what I'm really stuck with is when I want to edit a specific row, but I only have the available value lineid(for example 22), and not the row number in the array:

measurements.page[0].line[WHAT DO I PUT HERE].test = "new changed value";

Answer 1

you need to do a search

function find_in_array(arr, name, value) {
    for (var i = 0, len = arr.length; i<len; i++) {
        if (name in arr[i] && arr[i][name] == value) return i;
    };
    return false;
}

var id = find_in_array(measurements.page[0].line, 'lineid', 22);

Answer 2

You need to go through the array using a loop foruntil you find the element you need.

Answer 3

:

function getLinesByLineID( lines, id ) {
   var results = [];
   for( var i = 0, j = lines.length; i < j; i++ ) {
       if( lines[ i ].lineid === id ) {
          results.push( lines[ i ] ); 
       }
   }
   return ( results.length > 0 ) ? results : false;
}

: var lines = getLinesByID( json.page[0].line, 22 );