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'use strict'
module.exports = nGram
nGram.bigram = nGram(2)
nGram.trigram = nGram(3)
// Factory returning a function that converts a value string to n-grams.
function nGram(n) {
if (typeof n !== 'number' || isNaN(n) || n < 1 || n === Infinity) {
throw new Error('`' + n + '` is not a valid argument for n-gram')
}
return grams
// Create n-grams from a given value.
function grams(value) {
var nGrams = []
var index
if (value === null || value === undefined) {
return nGrams
}
value = value.slice ? value : String(value)
index = value.length - n + 1
if (index < 1) {
return nGrams
}
while (index--) {
nGrams[index] = value.slice(index, index + n)
}
return nGrams
}
}
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