How to use the acorn.tokTypes.comma function in acorn

lp.parseExprList = function(close, allowEmpty) {
  this.pushCx()
  let indent = this.curIndent, line = this.curLineStart, elts = []
  this.next() // Opening bracket
  while (!this.closes(close, indent + 1, line)) {
    if (this.eat(tt.comma)) {
      elts.push(allowEmpty ? null : this.dummyIdent())
      continue
    }
    let elt = this.parseMaybeAssign()
    if (isDummy(elt)) {
      if (this.closes(close, indent, line)) break
      this.next()
    } else {
      elts.push(elt)
    }
    this.eat(tt.comma)
  }
  this.popCx()
  if (!this.eat(close)) {
    // If there is no closing brace, make the node span to the start
    // of the next token (this is useful for Tern)

lp.parseExprList = function(close, allowEmpty) {
  this.pushCx()
  let indent = this.curIndent, line = this.curLineStart, elts = []
  this.next() // Opening bracket
  while (!this.closes(close, indent + 1, line)) {
    if (this.eat(tt.comma)) {
      elts.push(allowEmpty ? null : this.dummyIdent())
      continue
    }
    let elt = this.parseMaybeAssign()
    if (isDummy(elt)) {
      if (this.closes(close, indent, line)) break
      this.next()
    } else {
      elts.push(elt)
    }
    this.eat(tt.comma)
  }
  this.popCx()
  if (!this.eat(close)) {
    // If there is no closing brace, make the node span to the start
    // of the next token (this is useful for Tern)

node.superClass = this.eat(tt._extends) ? this.parseExpression() : null
  node.body = this.startNode()
  node.body.body = []
  this.pushCx()
  let indent = this.curIndent + 1, line = this.curLineStart
  this.eat(tt.braceL)
  if (this.curIndent + 1 < indent) { indent = this.curIndent; line = this.curLineStart }
  while (!this.closes(tt.braceR, indent, line)) {
    if (this.semicolon()) continue
    let method = this.startNode(), isGenerator, isAsync
    if (this.options.ecmaVersion >= 6) {
      method.static = false
      isGenerator = this.eat(tt.star)
    }
    this.parsePropertyName(method)
    if (isDummy(method.key)) { if (isDummy(this.parseMaybeAssign())) this.next(); this.eat(tt.comma); continue }
    if (method.key.type === "Identifier" && !method.computed && method.key.name === "static" &&
        (this.tok.type !== tt.parenL && this.tok.type !== tt.braceL)) {
      method.static = true
      isGenerator = this.eat(tt.star)
      this.parsePropertyName(method)
    } else {
      method.static = false
    }
    if (!method.computed &&
        method.key.type === "Identifier" && method.key.name === "async" && this.tok.type !== tt.parenL &&
        !this.canInsertSemicolon()) {
      isAsync = true
      isGenerator = this.options.ecmaVersion >= 9 && this.eat(tt.star)
      this.parsePropertyName(method)
    } else {
      isAsync = false

let node = this.startNode()
  node.properties = []
  this.pushCx()
  let indent = this.curIndent + 1, line = this.curLineStart
  this.eat(tt.braceL)
  if (this.curIndent + 1 < indent) { indent = this.curIndent; line = this.curLineStart }
  while (!this.closes(tt.braceR, indent, line)) {
    let prop = this.startNode(), isGenerator, start
    if (this.options.ecmaVersion >= 6) {
      start = this.storeCurrentPos()
      prop.method = false
      prop.shorthand = false
      isGenerator = this.eat(tt.star)
    }
    this.parsePropertyName(prop)
    if (isDummy(prop.key)) { if (isDummy(this.parseMaybeAssign())) this.next(); this.eat(tt.comma); continue }
    if (this.eat(tt.colon)) {
      prop.kind = "init"
      prop.value = this.parseMaybeAssign()
    } else if (this.options.ecmaVersion >= 6 && (this.tok.type === tt.parenL || this.tok.type === tt.braceL)) {
      prop.kind = "init"
      prop.method = true
      prop.value = this.parseMethod(isGenerator)
    } else if (this.options.ecmaVersion >= 5 && prop.key.type === "Identifier" &&
               !prop.computed && (prop.key.name === "get" || prop.key.name === "set") &&
               (this.tok.type != tt.comma && this.tok.type != tt.braceR)) {
      prop.kind = prop.key.name
      this.parsePropertyName(prop)
      prop.value = this.parseMethod(false)
    } else {
      prop.kind = "init"
      if (this.options.ecmaVersion >= 6) {

parseImportSpecifiers() {
    const nodes = [];
    let first = true;
    this.expect(tt.braceL);
    while (!this.eat(tt.braceR)) {
      if (first) {
        first = false;
      } else {
        this.expect(tt.comma);
        if (this.afterTrailingComma(tt.braceR)) break;
      }
      const node = this.startNode();
      node.view = this.eatContextual("viewof");
      if (!node.view) node.mutable = this.eatContextual("mutable");
      node.imported = this.parseIdent();
      if (this.eatContextual("as")) {
        node.local = this.parseIdent();
      } else {
        this.checkUnreserved(node.imported);
        node.local = node.imported;
      }
      this.checkLVal(node.local, "let");
      nodes.push(this.finishNode(node, "ImportSpecifier"));
    }
    return nodes;

isGenerator = this.options.ecmaVersion >= 9 && this.eat(tt.star)
      this.parsePropertyName(prop)
    } else {
      isAsync = false
    }
    if (isDummy(prop.key)) { if (isDummy(this.parseMaybeAssign())) this.next(); this.eat(tt.comma); continue }
    if (this.eat(tt.colon)) {
      prop.kind = "init"
      prop.value = this.parseMaybeAssign()
    } else if (this.options.ecmaVersion >= 6 && (this.tok.type === tt.parenL || this.tok.type === tt.braceL)) {
      prop.kind = "init"
      prop.method = true
      prop.value = this.parseMethod(isGenerator, isAsync)
    } else if (this.options.ecmaVersion >= 5 && prop.key.type === "Identifier" &&
               !prop.computed && (prop.key.name === "get" || prop.key.name === "set") &&
               (this.tok.type !== tt.comma && this.tok.type !== tt.braceR && this.tok.type !== tt.eq)) {
      prop.kind = prop.key.name
      this.parsePropertyName(prop)
      prop.value = this.parseMethod(false)
    } else {
      prop.kind = "init"
      if (this.options.ecmaVersion >= 6) {
        if (this.eat(tt.eq)) {
          let assign = this.startNodeAt(start)
          assign.operator = "="
          assign.left = prop.key
          assign.right = this.parseMaybeAssign()
          prop.value = this.finishNode(assign, "AssignmentExpression")
        } else {
          prop.value = prop.key
        }
      } else {

lp.parseExpression = function(noIn) {
  let start = this.storeCurrentPos()
  let expr = this.parseMaybeAssign(noIn)
  if (this.tok.type === tt.comma) {
    let node = this.startNodeAt(start)
    node.expressions = [expr]
    while (this.eat(tt.comma)) node.expressions.push(this.parseMaybeAssign(noIn))
    return this.finishNode(node, "SequenceExpression")
  }
  return expr
}

lp.parseExportSpecifierList = function() {
  let elts = []
  let indent = this.curIndent, line = this.curLineStart, continuedLine = this.nextLineStart
  this.pushCx()
  this.eat(tt.braceL)
  if (this.curLineStart > continuedLine) continuedLine = this.curLineStart
  while (!this.closes(tt.braceR, indent + (this.curLineStart <= continuedLine ? 1 : 0), line)) {
    if (this.isContextual("from")) break
    let elt = this.startNode()
    elt.local = this.parseIdent()
    if (isDummy(elt.local)) break
    elt.exported = this.eatContextual("as") ? this.parseIdent() : elt.local
    this.finishNode(elt, "ExportSpecifier")
    elts.push(elt)
    this.eat(tt.comma)
  }
  this.eat(tt.braceR)
  this.popCx()
  return elts
}