javascript - Reduce with obj key, value not working as expected

Question

I'm trying to dynamically create a sqlite insert string with node. I have:

function update_json_obj_into_table(tablename, obj, search_condition) {

  const insertValues = Object.entries(obj).reduce((acc, [k,v]) => acc.push(`${k} = ${v}`), []);

  const insertValuesString = Array.prototype.join.call(insertValues, '/');

 console.log(insertValuesString);
 console.log(`UPDATE ${tablename} SET ${insertValues} WHERE ${search_condition}`);
 // db.run(`UPDATE ${tablename} SET ${insertValuesString} WHERE search_condition ;`);
};

When I run it :

 const obj = {Code: 'A1'};
 update_json_obj_into_table('mytable', obj, 'search_condition') 

I get:

 UPDATE mytable SET 1 WHERE search_condition.

Obviously the insertValues is not working correctly. I was expecting:

Code = 1

but its coming out as '1' . What am I doing wrong?

question from:https://stackoverflow.com/questions/65649395/reduce-with-obj-key-value-not-working-as-expected

Answer 1

.push returns the new length of the array, not the mutated array. While you could put the .push on its own line and return the array on the next line:

function update_json_obj_into_table(tablename, obj, search_condition) {

  const insertValues = Object.entries(obj).reduce((acc, [k, v]) => {
    acc.push(`${k} = ${v}`);
    return acc;
  }, []);

  const insertValuesString = Array.prototype.join.call(insertValues, '/');

  console.log(insertValuesString);
  console.log(`UPDATE ${tablename} SET ${insertValues} WHERE ${search_condition}`);
  // db.run(`UPDATE ${tablename} SET ${insertValuesString} WHERE search_condition ;`);
};


const obj = {
  Code: 'A1'
};
update_json_obj_into_table('mytable', obj, 'search_condition')