How do I use the includes method in lodash to check if an object is in the collection

Question

lodash lets me check for membership of basic data types with includes     includes  1  2  3   2   gt  true   But the following doesn t work     includes    a   1     b   2      b   2    gt  false   This confuses me because the following methods that search through a collection seem to do just fine      where    a   1     b   2      b   2    gt    b   2    find    a   1     b   2      b   2    gt    b   2    What am I doing wrong   How do I check for the membership of an object in a collection with includes    edit   question was originally for for lodash version 2 4 1  updated for lodash 4 0 0

User · Answer

You could use find to solve your problem https   lodash com docs  find const data      quot a quot   1     quot b quot   2   const item     quot b quot   2    find data  item      gt  true

User · Answer

The includes  formerly called contains and include  method compares objects by reference  or more precisely  with       Because the two object literals of   b   2  in your example represent different instances  they are not equal  Notice      b   2        b   2    gt  false   However  this will work because there is only one instance of   b   2    var a     a   1   b     b   2     includes  a  b   b    gt  true   On the other hand  the where deprecated in v4  and find methods compare objects by their properties  so they don t require reference equality  As an alternative to includes  you might want to try some  also aliased as any      some    a   1     b   2      b   2    gt  true

User · Answer

Supplementing the answer by p s w g  here are three other ways of achieving this using lodash 4 17 5  without using   includes      Say you want to add object entry to an array of objects numbers  only if  entry does not exist already   let numbers           to  1  from  2          to  3  from  4          to  5  from  6          to  7  from  8          to  1  from  2      intentionally added duplicate     let entry     to  1  from  2            1  This will return the  index of the first  element that matches        findIndex numbers   o    gt    return   isMatch o  entry         output  0          2  This will return the entry that matches  Even if the entry exists       multiple time  it is only returned once        find numbers   o    gt    return   isMatch o  entry         output   to  1  from  2           3  This will return an array of objects containing all the matches        If an entry exists multiple times  if is returned multiple times        filter numbers    matches entry       output    to  1  from  2    to  1  from  2     If you want to return a Boolean  in the first case  you can check the index that is being returned     findIndex numbers   o    gt    return   isMatch o  entry      gt  -1     output  true

[javascript] How do I use the includes method in lodash to check if an object is in the collection?

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