Typescript Array OR Object

Question

I have this signature static cleanSOAP(envelope: [] | {}, removePassword: boolean = false) and after a constructor verification, if it's an Array I do a forEach on the envelope but, I got the error: Property 'forEach' does not exist on type '{} | []'. Property 'forEach' does not exist on type '{}'.ts(2339)

How can I prevent that ?

Code:

 static cleanSOAP(envelope: [] | {}, removePassword: boolean = false) {

    const unwantedProperties = ['$attributes'];

    if (removePassword === true) unwantedProperties.push('password');

    if (envelope && envelope.constructor === Array) {
      envelope.forEach(item: => {
        Helpers.cleanSOAP(item);
      });
    }

    else if (typeof envelope === 'object') {
      Object.getOwnPropertyNames(envelope)
        .forEach(key => {

          if (unwantedProperties.indexOf(key) !== -1) {
            delete envelope[key];
          }

          else if (envelope[key] === null) {
            delete envelope[key];
          }

          else if (envelope.hasOwnProperty(key) && typeof envelope[key] === 'object' && envelope[key] !== null && envelope[key].hasOwnProperty('$value')) {
            envelope[key] = envelope[key]['$value'];
          }

          else {
            Helpers.cleanSOAP(envelope[key]);
          }
        });
    }
  }

Can you show the rest of the code where you verify its type and call forEach? — John Montgomery
– John Montgomery, Commented Jun 8, 2020 at 23:35

CampbellMG · Accepted Answer · 2020-06-08 23:43:34Z

1

The forEach function doesn't exist on an object in typescript as you can't iterate an object directly. You need to determine if the parameter is either an array or object an then iterate accordingly. For example:

function cleanSOAP(envelope: [] | {}, removePassword: boolean = false){
   if(Array.isArray(envelope)){
       envelope.forEach(it => doSomething(it))
   } else {
       Object.keys(envelope).forEach(key => doSomething(evelope[key]))
   }
}

edited Jun 8, 2020 at 23:43

answered Jun 8, 2020 at 23:38

CampbellMG

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1 Comment

Jonathan Lafleur Over a year ago

Thank you ! My verification was not "strong enough" for TypeScript :) with isArray error disappeared.

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