[JavaScript]ShopifyCartAPIを叩く(change.js)

let sendData = {
    id         : item.key,
    quantity   : item.quantity,
    properties : {}
};
item.properties.forEach((property,index)=>{
    sendData.properties['プロパティ'+(index+1)] = property.value;
});
let options = {
    method       : 'POST',
    credentials  : 'same-origin',
    headers : {
        'Content-Type' : 'application/json'
    },
    body         : JSON.stringify(sendData)
};
fetch(window.Shopify.routes.root+'cart/change.js',options)
.then((response)=>{
    if (!response.ok) {
        throw new Error();
    }
    return response.json;
})
.then((json)=>{
    this.finishFetch();
})
.catch((error)=>{
    console.log(error);
});