js校验是否是数组

var is_array = function(value){return Object.prototype.toString.apply(value) == '[object Array]';
}

var b = [];

document.writeln(is_array(b));

Array.isArray(b) // 也可以使用

 指定数组的初始值

Array.dim = function(dimension,initial){var a = [], i;for(i = 0; i < dimension; i++){a[i] = initial;}return a;}var myArray =  Array.dim(10,"address");for(var i in myArray){document.writeln(myArray[i]);}

   js如何构建一个二维数组

Array.matrix = function (m, n, initial) {var a , i, j, mat = [];for(i = 0; i < m; i++){a = [];for(j = 0; j < n; j++){a[j] = initial;}mat[i] = a;}return mat;
}

js构建一个矩阵

Array.identity = function (n){var i, mat = Array.matrix(n, n, 0);for(i = 0; i < n; i++){mat[i][i] = 4;}return mat;
}
myMatrix = Array.identity(4);
document.writeln(myMatrix[3][3]);