I am trying to find an easy way to call parent function from child one. However, couldn't really found a way to directly call it from child instance as like in other programming languages.

class ExchangeHandler {
    constructor(getMarketsUrl, getMarketDataBaseUrl, interval) {
        this.interval = interval;
        this.getMarketsUrl = getMarketDataBaseUrl;
        this.getMarketDataBaseUrl = getMarketDataBaseUrl;
    }

    getMarketsUrl() {
        return this.getMarketsUrl;
    }

    getMarketDataBaseUrl() {
        return this.getMarketDataBaseUrl;
    }

    buildQueryUrl(params) {
        return querystring.stringify(params);
    }

    getIntervalParam() {
        return config.intervalToExchangeInput[[config.exchange]][[this.interval]];
    }
}

class BittrexHandler extends ExchangeHandler {
    constructor(interval) {
        super(".1/public/getmarkets", 
                ".0/pub/market/GetTicks", 
                interval);
    }

    buildGetMarketTickerUrl(symbol) {
        return super.getMarketDataBaseUrl() + "?"
                + super.buildQueryUrl({marketName: this.buildSymbolParam(symbol),
                                    tickInterval: super.getIntervalParam()})
    }

    buildSymbolParam(symbol) {
        return "BTC-" + symbol;
    }
}

var bittrexHandler = ExchangeHandlerFactory.getExchangeHandler("bittrex", "hour");
console.log("getMarketsUrl: " + bittrexHandler.getMarketsUrl());

And I get

TypeError: bittrexHandler.getMarketsUrl is not a function

Isn't this possible in javascript? Thanks a lot!

I am trying to find an easy way to call parent function from child one. However, couldn't really found a way to directly call it from child instance as like in other programming languages.

class ExchangeHandler {
    constructor(getMarketsUrl, getMarketDataBaseUrl, interval) {
        this.interval = interval;
        this.getMarketsUrl = getMarketDataBaseUrl;
        this.getMarketDataBaseUrl = getMarketDataBaseUrl;
    }

    getMarketsUrl() {
        return this.getMarketsUrl;
    }

    getMarketDataBaseUrl() {
        return this.getMarketDataBaseUrl;
    }

    buildQueryUrl(params) {
        return querystring.stringify(params);
    }

    getIntervalParam() {
        return config.intervalToExchangeInput[[config.exchange]][[this.interval]];
    }
}

class BittrexHandler extends ExchangeHandler {
    constructor(interval) {
        super("https://bittrex./api/v1.1/public/getmarkets", 
                "https://bittrex./Api/v2.0/pub/market/GetTicks", 
                interval);
    }

    buildGetMarketTickerUrl(symbol) {
        return super.getMarketDataBaseUrl() + "?"
                + super.buildQueryUrl({marketName: this.buildSymbolParam(symbol),
                                    tickInterval: super.getIntervalParam()})
    }

    buildSymbolParam(symbol) {
        return "BTC-" + symbol;
    }
}

var bittrexHandler = ExchangeHandlerFactory.getExchangeHandler("bittrex", "hour");
console.log("getMarketsUrl: " + bittrexHandler.getMarketsUrl());

And I get

TypeError: bittrexHandler.getMarketsUrl is not a function

Isn't this possible in javascript? Thanks a lot!

• javascript
• ecmascript-6
• es6-class

• You’re using super.methodName. Do you understand what the prototype is? – evolutionxbox Commented Apr 15, 2018 at 23:42
• @evolutionxbox I am trying to learn JS can you elaborate your question? – quartaela Commented Apr 16, 2018 at 0:04
• 1 I would remend you learn about JS prototypes – evolutionxbox Commented Apr 16, 2018 at 7:29

1 Answer 1

You can't have a data property and a method with the same name as you do with getMarketsUrl. They occupy the same property slot on the object. Change the name of one of them.

When you're trying to execute the method, the interpreter is finding the data property first and thus you can't call the method in the normal way.

In addition, you should not be using super to just call a non-overriden method on the object. For example, change this:

buildGetMarketTickerUrl(symbol) {
    return super.getMarketDataBaseUrl() + "?"
            + super.buildQueryUrl({marketName: this.buildSymbolParam(symbol),
                                tickInterval: super.getIntervalParam()})
}

to this:

buildGetMarketTickerUrl(symbol) {
    return this.getMarketDataBaseUrl() + "?"
            + this.buildQueryUrl({marketName: this.buildSymbolParam(symbol),
                                tickInterval: this.getIntervalParam()})
}