{"id":666,"date":"2023-03-01T20:23:34","date_gmt":"2023-03-01T20:23:34","guid":{"rendered":"https:\/\/freelance.in.th\/?p=666"},"modified":"2023-03-09T15:27:29","modified_gmt":"2023-03-09T15:27:29","slug":"javascript-how-to-check-duplicate-values","status":"publish","type":"post","link":"https:\/\/freelance.in.th\/index.php\/2023\/03\/01\/javascript-how-to-check-duplicate-values\/","title":{"rendered":"JavaScript : How to check duplicate values."},"content":{"rendered":"\n

To check for duplicate <\/strong>values in an array of objects<\/strong>, you can use the reduce()<\/em><\/strong><\/code> method to create an object where each key represents a unique value and the corresponding value is the number of times that value appears in the array. Here’s an example code snippet:<\/p>\n\n\n\n

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const data = [\n  {\n    \"id\": 1,\n    \"docNo\": \"doc123\",\n  },\n  {\n    \"id\": 2,\n    \"docNo\": \"doc456\",\n  },\n  {\n    \"id\": 3,\n    \"docNo\": \"doc123\",\n  }\n];\n\nconst docNoCounts = data.reduce((counts, obj) => {\n  counts[obj.docNo] = (counts[obj.docNo] || 0) + 1;\n  return counts;\n}, {});\n\nconsole.log(docNoCounts); \/\/ Output: { \"doc123\": 2, \"doc456\": 1 }\n<\/code><\/pre>\n<\/div>\n\n\n\n
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In this example, the reduce()<\/code><\/em><\/strong> method initializes an empty object as the initial value. Then, for each object in the array, it checks if the docNo<\/code> property already exists as a key in the object. If it does, it increments the count value by 1. If not, it adds the docNo<\/code> property as a new key in the object with an initial value of 1. Finally, the reduce()<\/em><\/strong><\/code> method returns the object with the count values for each docNo<\/code> value.<\/p>\n\n\n\n
You can then check if there are any duplicate values by iterating over the docNoCounts<\/code> object and checking if any of the values are greater than 1. For example:<\/p>\n\n\n\n
for (const docNo in docNoCounts) {\n  if (docNoCounts[docNo] > 1) {\n    console.log(`Duplicate docNo value found: ${docNo}`);\n  }\n}\n<\/code><\/pre>\n\n\n\n<\/a>\n","protected":false},"excerpt":{"rendered":"
To check for duplicate values in an array of objects, you can use the reduce() method to create an object where each key represents a unique value and the corresponding value is the number of times that value appears in the array. Here’s an example code snippet: In this example, the reduce() method initializes an…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[42],"tags":[43,44],"class_list":["post-666","post","type-post","status-publish","format-standard","hentry","category-programming","tag-javascript","tag-programming"],"_links":{"self":[{"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/posts\/666","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/comments?post=666"}],"version-history":[{"count":3,"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/posts\/666\/revisions"}],"predecessor-version":[{"id":737,"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/posts\/666\/revisions\/737"}],"wp:attachment":[{"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/media?parent=666"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/categories?post=666"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/freelance.in.th\/index.php\/wp-json\/wp\/v2\/tags?post=666"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}