Finds the elements of an array which satisfy a filter function. The original array is not affected.There is only a single signature for the grep function: $.grep(array, function(element, index) [,invert]). The function being passed in should return a truthy value or a falsy value based on the input argument. If the invert parameter is left out, or is false then the grep function will return a new array with all the items that the satisfy the truth test function that was passed in. If invert is set to true, grep will return a new array with all the items that do not satisfy the truth test function.
Lets take a look at looping through an array of text and removing the word "the":
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Now lets take a look at the same code, but with the invert parameter set to true:
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You'll see that only the word "the" is returned.
Check out the all of the jQuery function's of the week.