Angular 2 TypeScript how to get element in Array

Question

I need get element in a array by key.

const legendColors = {'On Hold': '#ef2e2e', 'Shipped': '#ff8e28', 'Complete': '#61c673', 'New': '#007cbb'};

...

return {name: v.name, value: v.value, color: legendColors[v.name]};

lint tool return this error on legendColors[v.name]:

ERROR in src/app/pages/orders/orders.composant.ts(46,62): error TS7017: Element implicitly has an 'any' type because type '{ 'On Hold': string; 'Shipped': string; 'Complete': string; 'New': string; }' has no index signature.

CRice · Accepted Answer · 2017-11-21 21:20:07Z

2

Typescript complains because there is no guarantee that v.name is one of the keys of legendColors, and there is no index signature. You can get past this by giving typescript a hint that v.name is in fact one of the keys:

return {name: v.name, value: v.value, color: legendColors[v.name as keyof typeof legendColors]};

or if legendColors adheres to an interface you already know the name of, you can simplify that a little:

return {name: v.name, value: v.value, color: legendColors[v.name as keyof SomeInterface]};

Finally, if you're actually not sure if v.name is a key of legendColors, then you'll actually have to add an index signature to it.

const legendColors: {[key: string]: string} = {'On Hold': '#ef2e2e', 'Shipped': '#ff8e28', 'Complete': '#61c673', 'New': '#007cbb'};

answered Nov 21, 2017 at 21:20

CRice

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