js 最大子串

function maxSub( arr ) {
	var SubMax = function ( start, end, sum ) {
		this.start = start;
		this.end = end;
		this.sum = sum;
	};
	SubMax.prototype.set = function ( submax ) {
		this.start = submax.start;
		this.end = submax.end;
		this.sum = submax.sum;
	};
	SubMax.prototype.subArr = function ( arr ) {
		return arr.slice( this.start , this.end + 1 );
	};
	var beforSubMax = new SubMax( 0, 0, arr[ 0 ] );
	var maxSubMax = new SubMax( 0, 0, arr[ 0 ] );
	for ( var i = 1 ; i < arr.length ; i++ ) {
		var tmp = beforSubMax.sum + arr[ i ];
		if ( tmp > arr[ i ] ) {
			beforSubMax.sum = tmp;
		} else {
			beforSubMax.sum = arr[ i ];
			beforSubMax.start = i;
		}
		beforSubMax.end = i;
		if ( beforSubMax.sum > maxSubMax.sum ) {
			maxSubMax.set( beforSubMax );
		}
	}
	return maxSubMax.subArr( arr );
}

//test you can test this on your web console
var array = [ 1, 3, -8, 9, 3, 13 ];
var result = maxSub( array );
console.log( result );