JavaScript: Search array of objects for a specific value

Question

Ok, so I have an array of objects. Which get defined with a randomly generated table value. I want to search the array of objects and execute code if one table value eg. "table1" occurs more than 6 times.

Here is the array of objects I have:

  var data = [{
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
                {
                    name: "",
                    pref: "",
                    table: ""
                },
            ];

the objects have all the same value, actually ... do you have a question? — Nina Scholz
– Nina Scholz, Commented Mar 2, 2017 at 21:31
Just run a filter on the array, data = data.filter ( x => { return x.name === 'value_I_want' } ). When it's done, if that array has a length >= 6, run your code. Alternatively if you don't want to allocate the new array, iterate the array, look for the property, increment a counter if you find it, when that counter is === 6, break out of the loop and run your code. — Tim Consolazio
– Tim Consolazio, Commented Mar 2, 2017 at 21:35

José Quinto Zamora · Accepted Answer · 2017-03-02 21:35:08Z

2

You can use this example:

if (data.filter((item)=>{return item.table === "1"}).length >= 6)

answered Mar 2, 2017 at 21:35

José Quinto Zamora

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3 Comments

jscoder001 Over a year ago

Great! Now can I use that same condition in a while loop?

Nina Scholz Over a year ago

no, you should not use filter for counting, it is the wrong method, because you generate a result array and refuse it later.

jscoder001 Over a year ago

@NinaScholz Oh, so if I use your method how can I use a while loop to run until the amount of table 1 values are less than 6?

Nina Scholz · Accepted Answer · 2017-03-03 07:43:14Z

1

You could use Array#reduce for counting with condition.

ES6

if (data.reduce((sum, item) => sum + (item.table === "1"), 0) > 6) {
    // do something
}

ES5

if (data.reduce(function (sum, item) { return sum + (item.table === "1"); }, 0) > 6) {
    // do something
}

... if I use your method how can I use a while loop to run until the amount of table 1 values are less than 6?

You could use a while loop with a closure over the value to check for.

function countTable(value) {
    return function (sum, item) {
        return sum + (item.table === value);
    };
}


while (data.reduce(countTable('table1'), 0) >= 6) {
    // do something
}

edited Mar 3, 2017 at 7:43

answered Mar 2, 2017 at 21:37

Nina Scholz

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6 Comments

jscoder001 Over a year ago

Ok, so I need this to change the table value until there are 6 or less 'table1' values. I have the while loop now how do I change the table value? Is there any way to do it similar to how you would do it in a for loop? Ex. data[i].table = "table2";

Nina Scholz Over a year ago

@jscoder001, please accept an answer before extending the question in the comments. i see actually no reason why and what property to change. you might as a new question with extended parameters.

jscoder001 Over a year ago

@NinaScholz Sorry, I'm new to SO, but I'm not as much asking you to change your code. I just need some guidance as to what to put inside the while loop. Should I ask this as another question?

Nina Scholz Over a year ago

it is more a question, what you wan. in the question, you ask for a occurrence of more than 6 times, now you need 6 or less. maybe you illustrate with an example what you need in a new question.

jscoder001 Over a year ago

Well, I'm checking for 6 or more and changing it until there are 6 or less. I'll ask another question though unless you think you have a quick solution.

|

traktor · Accepted Answer · 2017-03-02 23:26:13Z

0

You can also use Array.prototype.some to stop counting if sufficient matching elements have been found.

function multiFind( array, property, value , count) {
    return array.some( function( c) {
        count -= c[property] == value;
        return count<=0;
    });
}

Alternatively this could be compressed and written in ES6 syntax as

var multiFind =  (a, prop, v, n) => a.some( c=> (n-=c[prop] == v)<=0);

Note both versions use automatic type conversion to convert boolean true to 1 and false to 0 for counting purposes. A call to the function can then be used in a conditional statement such as.

while( multiFind( data, "table", "table1", 6) ) {
    // do stuff while there are more than 5 "table1" table properties in data array
}

edited Mar 2, 2017 at 23:26

answered Mar 2, 2017 at 23:20

traktor

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1 Comment

jscoder001 Over a year ago

Ok, I almost have it working. Any chance you could tell me how I could define a variable which would allow me to manipulate any value that is "table1"? I need to move the value to another table because each table may only have 6 occupants.

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