Javascript with Counting 
\n/**\n * @param {string} A\n * @param {string} B\n * @return {string[]}\n */\nvar uncommonFromSentences = function(A, B) {\n    let words = A.split(" ").concat
```\n/**\n * @param {string} A\n * @param {string} B\n * @return {string[]}\n */\nvar uncommonFromSentences = function(A, B) {\n    let words = A.split(" ").concat(B.split(" "));\n    let counts = {};\n    for(let i = 0; i < words.length; i++){\n        if(counts.hasOwnProperty(words[i]) === false)\n            counts[words[i]] = 0; \n        counts[words[i]]++;\n    }\n    \n    return words.filter(word => counts[word] === 1);\n};\n```
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