javascript - The "TypeError: Cannot convert undefined or null to object" when using filter method" in

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The code looks as following:

getSections () {
  if (!this.document) {
    return []
  }

  return Object.keys(this.document.Sections).filter(x => this.document.Sections[x])
}

The this.document.Sections is object that contains properties (objects as well).

How to get rid of this error?

The code looks as following:

getSections () {
  if (!this.document) {
    return []
  }

  return Object.keys(this.document.Sections).filter(x => this.document.Sections[x])
}

The this.document.Sections is object that contains properties (objects as well).

How to get rid of this error?

• javascript
• vue.js

Share Improve this question Follow edited Jun 20, 2019 at 13:44 demo 6,2451919 gold badges8383 silver badges158158 bronze badges asked Jun 20, 2019 at 13:07 tesicgtesicg 4,0631616 gold badges6868 silver badges127127 bronze badges 4

• 2 can you please confirm if this.document.Sections is a non-empty object, try consoling it. – akshay kishore Commented Jun 20, 2019 at 13:10
• I've updated the original post. Please, take a look above. – tesicg Commented Jun 20, 2019 at 13:12
• The code does in no way guarantee, that this.document.Sections is not undefined (or null, though unlikely), even after the update. – ASDFGerte Commented Jun 20, 2019 at 13:14
• 1 Does this answer your question? How to resolve TypeError: Cannot convert undefined or null to object – Donald Duck is with Ukraine Commented Aug 26, 2020 at 10:57

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4 Answers 4

Sorted by: Reset to default 4

As the message says, this error es from passing null to Object.keys. Try it in the console:

Object.keys(null)

VM198:1 Uncaught TypeError: Cannot convert undefined or null to object
    at Function.keys (<anonymous>)

So, in your code this.document.Sections is null.

Here you have an option to fix it. Hope it helps.

function getSections() {
    return (this.document && this.document.Sections)
        ? Object.keys(this.document.Sections)
            .filter(x => this.document.Sections[x])
        : [];
}

See it in a snippet:

var test = {
    document: {
        Sections: {
            a: 1,
            b: undefined,
            c: 3
        }
    }
};

function getSections() {
    return (test.document && test.document.Sections)
        ? Object.keys(test.document.Sections)
            .filter(x => test.document.Sections[x])
        : [];
}
console.log(getSections())

You need to check if this.document.Sections is null or undefined

getSections () {
  if (!this.document && !this.document.Sections) {
    return []
  }

  return Object.keys(this.document.Sections).filter(x => this.document.Sections[x])
}

[1,null,2,undefined,{},3].filter(x => isFinite(x) && x > 1) produces [2, 3]

[1,null,2,undefined,{},3].filter(x => x !== null && x != undefined) produces[1, 2, {}, 3]

Just specify the correct criteria in the filter.

That error could be more helpfully written as: "one of your variables was null or undefined"

There aren't many to choose from, but you will need to do a little local debugging to work out which, and why.

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