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Javascript console.log gives wrong result in variable

var cols = 9;
var rows = 9;
var matrix_empty = [];

for (var x = 0; x < cols; x++) {
    matrix_empty[x] = [];
    for (var y = 0; y < rows; y++) {
        matrix_empty[x][y] = -1;
    }
}
console.log(matrix_empty); //here give me wrong result not -1 in whole position

matrix_test = getRandomMatrix(matrix_empty);

function getRandomMatrix(matrix) {
    matrix[0][1] = 39;
    matrix[1][1] = 9;
    matrix[2][2] = 9;
    return matrix;
}

Question:

Why is the console log giving me the wrong result? They give me:

matrix[0][1] =39;
matrix[1][1] = 9;
matrix[2][2] = 9;

but I expect -1 in the whole matrix!

What should I do so that this gives me -1 in the entire matrix in console.log (set at this position)

I tested this in Firefox and Chrome.

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3 answers

Chrome , console.log, . , , console.log , JSON.stringify() - : console.log(JSON.stringify(matrix_empty)) BTW, matrix_empty , matrix_test, , matrix_test, matrix_empty. 2 , - : var matrix = $.extend(true,[],matrix_empty); 2 .

+1

( Chrome) console.log(). "matrix_empty" "getRandomMatrix()". JavaScript, , .

, , console.log() , console.log() . (edit — Firefox.)

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: -1 , getRandomMatrix. , , .

, , .

var cols = 9;
var rows = 9;
var matrix_empty = [];

function getRandomMatrix(matrix) {
    matrix[0][1] = 39;
    matrix[1][1] = 9;
    matrix[2][2] = 9;
    return matrix;
}

for (var x = 0; x < cols; x++) {
    matrix_empty[x] = [];
    for (var y = 0; y < rows; y++) {
        matrix_empty[x][y] = -1;
    }
}
console.clear(); // Just to empty the console so we don't confuse the results. 
console.log(matrix_empty); //here give me wrong result not -1 in whole position

setTimeout(function() { 
    matrix_test = getRandomMatrix(matrix_empty);
    console.log(matrix_empty);
}, 10000);

Let's start with a delay of 10 seconds, so that you have time to open the array in the debugger and make sure that the values ​​are really -1.

However, if you wait until the setTimeOut function starts in 10 seconds (or makes the timeout much shorter) without opening the array, after the second array is registered in the console, you can now open both arrays and make sure that yes , they were both changed. Another way to take a look at the introduction is to follow the vs pass by value link.

http://jsfiddle.net/vDgJ3/

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