handlebars compareTime helper

helper.js

Handlebars.registerHelper('compareTime', function(lhs, operator, rhs, options) {
        /*eslint eqeqeq: 0*/

        if (arguments.length < 4) {
            throw new Error('handlebars Helper {{compareTime}} expects 4 arguments');
        }

        var a = rhs, b = rhs;
        if (!moment.isMoment(a)) a = moment(lhs);
        if (!moment.isMoment(b)) b = moment(rhs);

        if (!a.isValid()) throw new Error('helper {{compareTime}}: invalid first input time: `' + lhs + '`');
        if (!b.isValid()) throw new Error('helper {{compareTime}}: invalid second input time: `' + rhs + '`');

        var result;
        switch (operator) {
            case '==':
            case '===':
            result = a.isSame(b);
            break;
            case '!=':
            case '!==':
            result = !(a.isSame(b));
            break;
            case '<':
            result = a.isBefore(b);
            break;
            case '>':
            result = a.isAfter(b);
            break;
            case '<=':
            result = a.isSameOrBefore(b);
            break;
            case '>=':
            result = a.isSameOrAfter(b);
            break;
            default: {
            throw new Error('helper {{compareTime}}: invalid operator: `' + operator + '`');
            }
        }

        if (result === false) {
            return options.inverse(this);
        }
        return options.fn(this);
    });