copy(matrix) {
        const array = matrix.elements;
        this.elements[0] = array[0];
        this.elements[1] = array[1];
        this.elements[2] = array[2];
        this.elements[3] = array[3];
        this.elements[4] = array[4];
        this.elements[5] = array[5];
        this.elements[6] = array[6];
        this.elements[7] = array[7];
        this.elements[8] = array[8];
        this.elements[9] = array[9];
        this.elements[10] = array[10];
        this.elements[11] = array[11];
        this.elements[12] = array[12];
        this.elements[13] = array[13];
        this.elements[14] = array[14];
        this.elements[15] = array[15];

        return this;
    }
Copy another Mat4

     params:
     @matrix (Mat4 class object): matrix to copy

     returns:
     @this (Mat4 class object): this matrix after copy
*