Javascript check deeply nested field exists

Asked May 13 '20 at 14:25

Active May 13 '20 at 14:25

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I have a problem where I have data (returned from an API so I have no control over it) and I want to retrieve a value that is deeply nested within the data, but might not exist. For example, if the data looks like this:

const data = { level1: { level2: { level3: { level4: "value" } } } };

To get the value when I don't know if it exists I have to do:

const value =
  level1 && level1.level2 && level1.level2.level3 && level1.level2.level3.level4
    ? level1.level2.level3.level4.value
    : "missing";

Which becomes unwieldy and very hard to read when you have more levels and longer key names.
Is there a better way I can check whether a deeply nested value exists? vanilla JS please.

asked May 13 '20 at 14:25

Max888

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You can use a recursive function for that. – Ramesh Reddy May 13 '20 at 14:27
You can also cache levels in variables (i.e. `const level4 = data.level1.level2.level3.level4;`), which makes subsequent tests easier (i.e. `level4.value`). – Scott Marcus May 13 '20 at 14:29

Javascript check deeply nested field exists

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