three.js/examples/js/lines/Wireframe.js

( function () {

	const _start = new THREE.Vector3();
	const _end = new THREE.Vector3();
	class Wireframe extends THREE.Mesh {

		constructor( geometry = new THREE.LineSegmentsGeometry(), material = new THREE.LineMaterial( {
			color: Math.random() * 0xffffff
		} ) ) {

			super( geometry, material );
			this.isWireframe = true;
			this.type = 'Wireframe';

		}

		// for backwards-compatibility, but could be a method of THREE.LineSegmentsGeometry...

		computeLineDistances() {

			const geometry = this.geometry;
			const instanceStart = geometry.attributes.instanceStart;
			const instanceEnd = geometry.attributes.instanceEnd;
			const lineDistances = new Float32Array( 2 * instanceStart.count );
			for ( let i = 0, j = 0, l = instanceStart.count; i < l; i ++, j += 2 ) {

				_start.fromBufferAttribute( instanceStart, i );
				_end.fromBufferAttribute( instanceEnd, i );
				lineDistances[ j ] = j === 0 ? 0 : lineDistances[ j - 1 ];
				lineDistances[ j + 1 ] = lineDistances[ j ] + _start.distanceTo( _end );

			}

			const instanceDistanceBuffer = new THREE.InstancedInterleavedBuffer( lineDistances, 2, 1 ); // d0, d1

			geometry.setAttribute( 'instanceDistanceStart', new THREE.InterleavedBufferAttribute( instanceDistanceBuffer, 1, 0 ) ); // d0
			geometry.setAttribute( 'instanceDistanceEnd', new THREE.InterleavedBufferAttribute( instanceDistanceBuffer, 1, 1 ) ); // d1

			return this;

		}

	}

	THREE.Wireframe = Wireframe;

} )();