constructor( size = 10, divisions = 10, color1 = 0x444444, color2 = 0x888888 ) {

		color1 = new Color( color1 );
		color2 = new Color( color2 );

		const center = divisions / 2;
		const step = size / divisions;
		const halfSize = size / 2;

		const vertices = [], colors = [];

		for ( let i = 0, j = 0, k = - halfSize; i <= divisions; i ++, k += step ) {

			vertices.push( - halfSize, 0, k, halfSize, 0, k );
			vertices.push( k, 0, - halfSize, k, 0, halfSize );

			const color = i === center ? color1 : color2;

			color.toArray( colors, j ); j += 3;
			color.toArray( colors, j ); j += 3;
			color.toArray( colors, j ); j += 3;
			color.toArray( colors, j ); j += 3;

		}

		const geometry = new BufferGeometry();
		geometry.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );
		geometry.setAttribute( 'color', new Float32BufferAttribute( colors, 3 ) );

		const material = new LineBasicMaterial( { vertexColors: true, toneMapped: false } );

		super( geometry, material );

		this.type = 'GridHelper';

	}
Constructs a new grid helper.

@param {number} [size=10] - The size of the grid.
@param {number} [divisions=10] - The number of divisions across the grid.
@param {number|Color|string} [color1=0x444444] - The color of the center line.
@param {number|Color|string} [color2=0x888888] - The color of the lines of the grid.