safeReference

var falafel = require('falafel');

function safeReference(ex) {
    var nodes = {
        members: [],
        objects: [],
        declarator: ""
    };

    falafel(ex, function(node) {

        if (node.type == "VariableDeclaration") {
            nodes.declarator = node.source()
        }
        if (node.type === "MemberExpression") {
            nodes.objects.push(node.object.source());
            nodes.members.push("(" + node.source() + ")")
        }
    });

    nodes.members.unshift(nodes.objects[0]);
    var splitedDeclarator = nodes.declarator.split(' = ');
    splitedDeclarator[1] = nodes.members.join(' && ');

    nodes.declarator = splitedDeclarator.join(' = ') + ';';
    return nodes.declarator;
}


var src = 'var x = a.b.c.d;';
console.log(safeReference(src));