Function transformVarsToLetOrConst

src/transform/let.js:145–189

()

// This is where the actual transform happens
function transformVarsToLetOrConst() {
  getFunctionVariableGroups().forEach(group => {
    // Do not modify existing let & const
    if (group.getNode().kind !== 'var') {
      return;
    }

    if (isLexicalVariableProhibited(group)) {
      logWarningForVarKind(group.getNode());
      return;
    }

    const commonKind = group.getCommonKind();
    if (commonKind) {
      // When all variables in group are of the same kind,
      // just set appropriate `kind` value for the existing
      // VariableDeclaration node.
      group.getNode().kind = commonKind;
      logWarningForVarKind(group.getNode());
    }
    else if (hasMultiStatementBody(group.getParentNode())) {
      // When some variables are of a different kind,
      // create separate VariableDeclaration nodes for each
      // VariableDeclarator and set their `kind` value appropriately.
      const varNodes = group.getVariables().map(v => {
        return new VariableDeclaration(v.getKind(), [v.getNode()]);
      });

      multiReplaceStatement({
        parent: group.getParentNode(),
        node: group.getNode(),
        replacements: varNodes,
        preserveComments: true,
      });

      logWarningForVarKind(group.getNode());
    }
    else {
      // When parent node restricts breaking VariableDeclaration to multiple ones
      // just change the kind of the declaration to the most restrictive possible
      group.getNode().kind = group.getMostRestrictiveKind();
      logWarningForVarKind(group.getNode());
    }
  });
}

// let and const declarations aren't allowed in all the same places where
// var declarations are allowed. Notably, only var-declaration can occur