For the first time I met this method of setting a variable. I'm a little tangled up with double brackets. What does this mean?
var defaultState = (0, _state2.default)(servicePath, stateOptions);
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Alexandr Lukovnikov
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Where have you seen the code. Can you please tell the purpose and context of code? – Maheer Ali May 18 '19 at 03:31
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I seen it in feathers-vuex https://www.npmjs.com/package/feathers-vuex – Alexandr Lukovnikov May 18 '19 at 03:36
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1Maybe next link can help to understand when that can be useful: https://stackoverflow.com/questions/40967162/what-is-the-meaning-of-this-code-0-function-in-javascript – Shidersz May 18 '19 at 03:38
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(0, _state2.default) is an expression which contains comma operator. It evaluates to its last operand. Here _state2.default is last operand. So
(0, _state2.default)(servicePath, stateOptions);
Is same as
_state2.default(servicePath, stateOptions);
The second brackets call the function with two arguments.
The first () are used to group an expression. While the second () are used to call the function.
Maheer Ali
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2But why would we use it like this? We can call `_state2.default(servicePath, stateOptions);` directly, or `(_state2.default)(servicePath, stateOptions);` if we want to keep the brackets. – R Xy May 18 '19 at 03:24