Property 'map' does not exist on type 'State' React code example

Example 1: Property 'state' does not exist on type

Can be multiple reasons. Main ones are missing @types/react in Dependencies

try typing this in the terminal (make sure it's the terminal of the right 
folder):

npm install --save-dev @types/react @types/react-dom

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Example 2: property 'map' does not exist on type 'object'

if (myStructure instanceof Array) {
    myStructure.map((val, idx, []) => { });
}