UnhandledPromiseRejectionWarning: TypeError: 无法读取未定义的属性“forEach”

Question

My code :

export const convertToTickerObject = (data) => {
  const keys = [
    'id',
    'last',
    'lowestAsk',
    'highestBid',
    'percentChange',
    'baseVolume',
    'quoteVolume',
    'isFrozen',
    'high24hr',
    'low24hr'
  ];

  const object = {};
  data.forEach((value, i) => {
    if (i === 0) {
      object.name = getCurrencyPairId(value);
      return; //escape arrow function
    }
    const key = keys[i];
    object[key] = value;
  });

  return object;
};

Error:

UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'forEach' of undefined UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1) (node:7188) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

I try use async/await, but this warning continuously occured.

How can I solve this warning ? :(

Answer 1

As it says in the error, the parameter you pass is probably undefined or not an object. Try this:

 const convertToTickerObject = (data) => { if ( typeof data !== 'object' ){ return 'Not object. Parameter type: '+ typeof data; } if( Object.keys(data).length === 0 && data.constructor === Object ){ return 'object empty'; } const keys = [ 'id', 'last', 'lowestAsk', 'highestBid', 'percentChange', 'baseVolume', 'quoteVolume', 'isFrozen', 'high24hr', 'low24hr' ]; const object = {}; data.forEach((value, i) => { if (i === 0) { object.name = getCurrencyPairId(value); return; //escape arrow function } const key = keys[i]; object[key] = value; }); return object; };

This may reveal where a mistake somewhere else. It would be good to have checks like the ones I added in place anyway.