Handlebars: How to make custom helper for sum array? - handlebars.js

Question

I try like this:
sum: function(arr) {
const s = 0;
for(const i=0; i<arr.length; i++) {
s = s + arr[i];
}
return s;
}
and output that in table like this:
{{#each something}}
<td>{{sum this}}</td>
{{/each}}
but in this case nothing appears, any suggestions?
[this] array contains numbers
50 | 10 | 10 | 10 | 5 | 5 |
60 | 10 | 10 | 10 | 5 | 5 |
50 | 10 | 10 | 10 | 10 | 10|
so result should be
160 | 30 | 30 | 30 | 20 | 20 |
but in my method return zero values.
If I do as #Christophe Thiry show me:
sum: function(item) {
result = item[0]
for (i=0; i<result.length; i++) {
for (j=1; j<item.length; j++) {
result[i] = result[i]+item[j][i];
}
}
return result.toString();
}
and just:
<td>{{sum this}}</td>
I get TypeError: Cannot read property 'length' of undefined
Schema model:
const StateResultSchema = new Schema({
electoralUnit: {
type: Schema.Types.ObjectId,
ref: 'ElectoralUnit',
required: true,
unique: true
},
allVotes: {
type: Number,
required: true
},
validVotes: {
type: Number,
required: true
},
invalidVotes: {
type: Number,
required: true
},
partyVotes: {
type: [Number],
required: true
}
});
this is how it look like in MongoDB Compass"
_id:ObjectId("5ac4e01d46fa2b21280bd981")
electoralUnit:ObjectId("5ab906612f30fe23dc592591")
allVotes:100
validVotes:90
invalidVotes:10
partyVotes:[50,10,10,10,5,5]
__v:0

Answer 1

You don't need the each helper, you have to use the helper that you've created directly so {{sum something}} and also review your sum helper because you iterate only over one array.
Look at the below snippet to see how to achieve that.
$(document).ready(function () {
var context = { "something" : [
{ "_id":"5ac4e01d46fa2b21280bd981", "electoralUnit":"5ab906612f30fe23dc592591", "allVotes":100, "validVotes":90, "invalidVotes":10, "partyVotes":[50,10,10,10,5,5], "__v":0},
{ "_id":"5ac4e01d46fa2b21280bd982", "electoralUnit":"5ab906612f30fe23dc592592", "allVotes":100, "validVotes":90, "invalidVotes":10, "partyVotes":[50,10,10,10,5,5], "__v":0},
{ "_id":"5ac4e01d46fa2b21280bd983", "electoralUnit":"5ab906612f30fe23dc592593", "allVotes":100, "validVotes":90, "invalidVotes":10, "partyVotes":[60,10,10,10,5,5 ], "__v":0},
{ "_id":"5ac4e01d46fa2b21280bd984", "electoralUnit":"5ab906612f30fe23dc592594", "allVotes":100, "validVotes":90, "invalidVotes":10, "partyVotes":[50,10,10,10,10,10], "__v":0}
]
};
Handlebars.registerHelper('sum', function(item) {
result = item[0].partyVotes;
for (i=0; i<result.length; i++) {
for (j=1; j<item.length; j++) {
result[i] = result[i]+item[j].partyVotes[i];
}
}
return result.toString();
});
var source = $("#sourceTemplate").html();
var template = Handlebars.compile(source);
var html = template(context);
$("#resultPlaceholder").html(html);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/handlebars.js/4.0.5/handlebars.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script id="sourceTemplate" type="text/x-handlebars-template">
{{sum something}}
</script>
<br/>
<div id="resultPlaceholder">
</div>