trepanjs/lib/eval.js

A gdb-like debugger for nodejs. It is in the style of the trepanning debuggers.

// extract the "expression" part of a line of source code.
function extract_expression(text) {
  if (text.match(/^\s*(?:if|while)\s+\((.+)\)\s*{/)) {
    text = text.replace(/^\s*(?:if|while)\s+\((.+)\)\s*{.*$/, '$1');
  } else if (text.match(/^\s*return\s+/)) {
    // EXPRESION in: return EXPRESSION
    text = text.replace(/^\s*return\s+/, '');
  } else if (text.match(/^\s*(?:var\s)?[A-Za-z_][A-Za-z0-9_\[\]]*\s*=[^=;]/)) {
    // RHS of an assignment statement.
    text = text.replace(/^\s*(?:var\s)?\s*[A-Za-z_][A-Za-z0-9_\[\]]*\s*=\s*(.+)[;,]$/, '$1');
  }
  return text;
}
exports.extract_expression = extract_expression;

if (process.argv[1] == __filename) {
  var stmts = ['var id = rhs;',
               'if (condition(x)) { return null };',
	       'while (expression) {',
	       'return return_value;',
	       'lhs = rhs;',
	       'var x = 5,',
	       'nothing_to_be.done'];
  for (var i in stmts) {
    console.log(extract_expression(stmts[i]));
  }
}