CODEWITHSUNDEEP
javascriptarraysnode.js
Jagadeesh
Jagadeesh

Reputation: 2097

how to push the result of each element in an array to a global variable in javascript nodejs?

var container = [];

var number = ['1234567890', '646494964', '4498549646', '46654654664', '546646546']

for (k = 0; k < number.length; k++) {

    var sql1 = "SELECT name,age FROM  `table` WHERE  `mobile_number` LIKE '%" + number[k] + "%'"

    mysql.query(sql1, function(error, result) {
        // I will be getting the result of first element in the array here
        console.log(result);
        container.push(result);
    });
}

I need to push the result of each element in the array to the container variable. i need something like.

var container = [{name:"steve",age:"22"},{name:"john",age:"22"},{name:"boss",age:"24"},{name:"jeff",age:"28"},{name:"michael",age:"29"}]

Upvotes: 2

Views: 1545

Answers (3)

Redu
Redu

Reputation: 26161

Well I don't know if mySQL.query() function returns a Promise object or not. Assuming that it doesn't, lets try to simulate our mySQL database which includes a query method which would return a result asynchronously within 200ms.

mySQL = { '1234567890' : {name: "John Doe", age: 22},
          '646494964'  : {name: "Mary Jones", age: 28},
          '4498549646' : {name: "Sam Johnson", age: 44},
          '46654654664': {name: "Terry Gibson", age: 18},
          '546646546'  : {name: "Patricia Snow", age: 31},
          query        : function(q,cb){
                           setTimeout(function(db){
                                        var result = db[q];
                                        !!result ? cb(false,result)
                                                 : cb("Nothing found for query #: " + q, void 0);
                                      }, Math.random()*200, this);
                         }
         }

Now the following snippet will promisify any asynchronous call which takes a data and an error first type callback (cb(err, res)).

function promisify(fun){
  return function(data){
           return new Promise((v,x) => fun(data, (err,data) => !!err ? x(err)
                                                                     : v(data)));
         }
}

Once we promisify mySQL.query like promisfy(mySQL.query.bind(mySQL))it will start returning promises. (We use bind here since when the fun argument variable of the promisify function gets assigned to mySQL.query, it will invoke mySQL.query with the this as promisify's scope and we don't want that. So we secure fun to be bound to mySQL all the time. (Bonus JS knowledge here..!)

Well OK we are almost ready, let's wrap it yup and "sequentially" query our matchstick DB which supports promises. In order to sequentially tie a series of promise-returning-queries in an array, it's best to use a .reduce() to chain up the .then() stages of the previous query to the next. Cool..!

function promisify(fun){
  return function(...data){
           return new Promise((v,x) => fun(...data, (err,data) => !!err ? x(err) : v(data)));
         };
}

function mysqlQuery(query,cb){
  setTimeout(function(){
               var result = database[query];
               !!result ? cb(false,result) : cb("Nothing found for query #: " + query, void 0);
             }, Math.random()*200);
}

var numbers  = ['1234567890', '646494964', '122', '4498549646', '46654654664', '546646546'],
    mySQL    = { '1234567890' : {name: "John Doe", age: 22},
                 '646494964'  : {name: "Mary Jones", age: 28},
                 '4498549646' : {name: "Sam Johnson", age: 44},
                 '46654654664': {name: "Terry Gibson", age: 18},
                 '546646546'  : {name: "Patricia Snow", age: 31},
                 query        : function(q,cb){
                                  setTimeout(function(db){
                                               var result = db[q];
                                               !!result ? cb(false,result)
                                                        : cb("Nothing found for query #: " + q, void 0);
                                               }, Math.random()*200, this);
                                }
                },
    contents = [];
                
numbers.reduce((p,n) => p.then(c => promisify(mySQL.query.bind(mySQL))(n))
                         .then(d => contents.push(d), e => console.log(e)), Promise.resolve())
       .then(_ => console.log(contents));
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 1

Jaromanda X
Jaromanda X

Reputation: 1

As mentioned in another answer, the more performant way to do this is a single query, built up in a loop

var number = ['1234567890', '646494964', '4498549646', '46654654664', '546646546']

var sqlPre = "SELECT name,age FROM  `table` WHERE";
var sqlArray = number.map(item => "`mobile_number` LIKE '%" + item + "%'");
var sql1 = `${sqlPre} ${sqlArray.join(" OR ")}`;
mysql.query(sql1, function(error, result) {
    container = result.map(({name, age}) => ({name, age}));
});

Note: the above uses many ES2015+ concepts, if they are unfamiliar to you, then in ES5 it would be

var number = ['1234567890', '646494964', '4498549646', '46654654664', '546646546'];

var sqlPre = "SELECT name,age FROM  `table` WHERE";
var sqlArray = number.map(function (item) {
    return "`mobile_number` LIKE '%" + item + "%'";
});
var sql1 = sqlPre + ' ' + sqlArray.join(" OR ");
mysql.query(sql1, function (error, result) {
    container = result.map(function (_ref) {
        var name = _ref.name,
            age = _ref.age;
        return { name: name, age: age };
    });
});

I'm assuming that results is an array of objects, I don't know how mysql in nodejs works

Upvotes: 1

aSoler
aSoler

Reputation: 145

container.push({name: result.name, age: result.age}));

I think it could help. But I recommend you to do a single query.

"SELECT name,age FROM table WHERE mobile_number IN (" + number.join(',') + ")"

Upvotes: 1

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