get sponsor signature function

getSponsorSignature.js

// HTTP function definition
async function getSponosrSignature(sender, txBody) {
    const url = 'http://localhost:3000/'
    const response = await fetch(url, {
        method: 'POST',
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        },
        body: JSON.stringify({
            'sender': sender,
            'txBody': txBody
        })
    })

    const r = await response.json()
    return r['sponsor_signature']
}

// Fetch the sponsor signature.
const sponsorSignature = await getSponosrSignature(
    '0x'+originAddress.toString('hex'),
    txBody
)