Quick BST Implementation

BST.js

var BST = function(arr){
    var length = arr.length,
        middle = length % 2 === 0 ? length/2 : (length -1)/2;
    this.value = arr[middle];
    if(length > 1) {
        this.left = new BST(arr.slice(0, middle ));
        this.right = new BST(arr.slice((middle + 1), length));
    }
}

BST.prototype.search = function(value) {
    if (this.value === value) {
        return value;
    } else if(this.left && this.value > value) {
        return this.left.search(value);
    } else if (this.right && this.value < value) {
        return this.right.search(value);
    } else {
        return null;
    }
}