Introduction

Yes! I understand a bit about TypeScript. I want to save this knowledge for my upcoming job. I can use that for Java and Swift…

This code is commented not “beautiful”. Here is the code:

function getSrcTokensAndDestTokens(network) {
    const tokenInputs = this.srcTokens.concat(this.destTokens);

    for (const token of tokenInputs) {
        if (network.tokens[token].hidden || network.tokens[token].delisted) {
            console.log(`GSI doesn't support ${token} yet!`);
            return;
        }
    }

    if (this.srcTokens.length === 0 && this.destTokens.length === 0) {
        console.error("srcTokens and destTokens can't be both empty!");
        return;
    }

    if (this.srcTokens.length === 0) {
        for (const token in network.tokens) {
            if (!network.tokens[token].hidden && !network.tokens[token].delisted) {
                this.srcTokens.push(token);
            }
        }
    }

    if (this.destTokens.length === 0) {
        for (const token in network.tokens) {
            if (!network.tokens[token].hidden && !network.tokens[token].delisted) {
                this.destTokens.push(token);
            }
        }
    }
    // ...
    return {
        // ...
    }
}

Here is how to make it more beautiful.

1

This method implementation is long.

function getSrcTokensAndDestTokens(network)

What is src dest ? So, let’s change the function name

function getSourceTokensAndDestinationTokens(...)

or

function getSourceAndDestinationTokens(...)

… and

const tokenInputs = this.srcTokens.concat(this.destTokens);

=> const tokenInputs = this.sourceTokens.concat(this.destinationTokens);

2

We have a for-loop and an if for checking error here. hidden and delisted are not a good name for boolean values.

for (const token of tokenInputs) {
    if (network.tokens[token].hidden ||
        network.tokens[token].delisted) {
        console.log(`GSI doesn't support ${token} yet!`);
        return;
    }
}

Refactor

const token = network.tokens[tokenInput] // #1
if (token.isHidden || token.isDelisted) {
    // ...
}

Next, This log is hard to search. The output log looks like:

GSI doesn't support ewqdfsfgmvnxdlmfnvmldmswldld yet!
GSI doesn't support ljdilhKHKJBJHJGVKUYIlJNKJNBH yet!
GSI doesn't support KJHJK yet!

Now, let refactor

const ERROR_LOG_NOT_SUPPORTED_TOKEN = "Token not supported"
function isValidTokenInputs(network, tokenInputs) {
    for (const tokenInput in tokenInputs) {
        const token = network.tokens[tokenInput]
        if (token.isHidden || token.isDelisted) {
            return [false, tokenInput] // We should create a type instead of using an array or
                                       // a pair because it looses context information
        }
    }

    return [true, ""]
}
function getSrcTokensAndDestTokens(network) {
    // ...
    const [isSourceTokenValid, wrongSourceTokenInput] =
            isValidTokenInputs(network, tokenInputs)
    if (!isSourceTokenValid) {
        console.log(ERROR_LOG_NOT_SUPPORTED_TOKEN, wrongSourceTokenInput)
        return
    }
    //...
}

3

We have depth nested block here.

if (this.srcTokens.length === 0) {
    for (const token in network.tokens) {
        if (!network.tokens[token].hidden &&
            !network.tokens[token].delisted) {
            this.srcTokens.push(token);
        }
    }
}
if (this.destTokens.length === 0) {
    for (const token in network.tokens) {
        if (!network.tokens[token].hidden &&
            !network.tokens[token].delisted) {
            this.destTokens.push(token);
        }
    }
}

We should define a method to check a token is valid or not

function isTokenValid(token) {
    return !token.isHidden && !token.isDelisted
}

… define method for get valid

function getValidTokens(tokens) {
    const result = []
    for (const token in tokens) {
        if (isTokenValid(token) {
            result.push(token)
        }
    }
}

and the two if-s will be

const validNetworkTokens = getValidTokens(network.tokens) // #1
if (this.sourceTokens.length === 0) {
    this.sourceTokens = validNetworkTokens // #2
}
if (this.destinationTokens.length === 0) {
    this.destinationTokens = validNetworkTokens // #2
}

Updating …