js DNA dynamic sequence alignment code_javascript skills

<title>Dynamic sequence alignment</title>
[Ctrl A to select all Note: If you need to introduce external Js, you need to refresh to execute

]<script> function pairaln(seq1, seq2){ // scoring scheme var MATCH = 1; // +1 for letters that match var MISMATCH = -1; // -1 for letters that mismatch var GAP = -1; // -1 for any gap // initialization var score=[[]]; var pointer=[[]]; score[0][0] = 0; pointer[0][0] = 0; var l1=seq1.length var l2=seq2.length for(var j = 1; j <= l1; j++) { score[0][j] = GAP * j; pointer[0][j] = 2; } for (var i = 1; i <= l2; i++) { score[i]=[]; pointer[i]=[]; score[i][0] = GAP * i; pointer[i][0] = 3; } // fill for(var i = 1; i <= l2; i++) { var letter2 = seq2.charAt(i-1); for(var j = 1; j <= l1; j++) { var diagonal_score, left_score, up_score; // calculate match score var letter1 = seq1.charAt(j-1); if (letter1 == letter2) { diagonal_score = score[i-1][j-1] + MATCH; } else { diagonal_score = score[i-1][j-1] + MISMATCH; } // calculate gap scores up_score = score[i-1][j] + GAP; left_score = score[i][j-1] + GAP; // choose best score if (diagonal_score >= up_score) { if (diagonal_score >= left_score) { score[i][j] = diagonal_score; pointer[i][j] = 1; } else { score[i][j] = left_score; pointer[i][j] = 2; } } else { if (up_score >= left_score) { score[i][j] = up_score; pointer[i][j] = 3; } else { score[i][j] = left_score; pointer[i][j] = 2; } } } } // trace-back var align1 = []; var align2 = []; // start at last cell of matrix var j = l1; var i = l2; while (1) { if(pointer[i][j] == 0)break // ends at first cell of matrix if (pointer[i][j] == 1) { align1[align1.length] = seq1.charAt(j-1); align2[align2.length] = seq2.charAt(i-1); i--; j--; } if (pointer[i][j] == 2) { align1[align1.length] = seq1.charAt(j-1); align2[align2.length] = "-"; j--; } if (pointer[i][j] == 3) { align1[align1.length] = "-"; align2[align2.length] = seq2.charAt(i-1); i--; } } align1 = align1.reverse(); align2 = align2.reverse(); return "序列：<p>"+seq1+"<br>"+seq2+"<p>比对结果：<table><tr><td>"+align1.join("<td>")+"<tr><td>"+align2.join("<td>")+"" } document.write(pairaln('CTGGGCTGACTGA', 'GACTAGCTAGACTGA')) </script>