indexOf

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2023-12-01

Performs (at worst) a linear search from the head of this sequence, returning the first index at which the specified value is found.

Signature

Sequence.indexOf = function(value, equalityFn) { /*...*/ }

Sequence.indexOf = function indexOf(value, equalityFn) {
  var eq = equalityFn || Lazy.equality,
  foundIndex = -1;

  this.each(function(e, i) {
if (eq(e, value)) {
  foundIndex = i;
  return false;
}
  });
  return foundIndex;
}

Name	Type(s)	Description
value	*	The element to search for in the sequence.
equalityFn	Function?	An optional equality function, which should take two arguments and return true or false to indicate whether those values are considered equal.
returns	number	The index within this sequence where the given value is located, or -1 if the sequence doesn't contain the value.

Examples

function reciprocal(x) { return 1 / x; }

Lazy(["foo", "bar", "baz"]).indexOf("bar")   // => 1
Lazy([1, 2, 3]).indexOf(4)                   // => -1
Lazy([1, 2, 3]).map(reciprocal).indexOf(0.5) // => 1