React JS maintain array inside state

Issue is you are updating the state value in a wrong way, Update the state value like this:

this.setState({
     terms: this.state.terms,
     myArray : this.state.myArray
});

As per DOC:

Never mutate this.state directly, as calling setState() afterwards may replace the mutation you made. Treat this.state as if it were immutable.

Update the state array like this, first create a copy of that by using slice(), then do the change and use setState to update:

let arr = this.state.myarr.slice();
arr.push('data');
this.setState({arr});

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