You can use JSON Logic to create complex calculated values based on the values of other fields.
Formio.createForm(document.getElementById('formio'), {
components: [
{
type: 'number',
label: 'A',
key: 'a',
input: true,
inputType: 'text',
multiple: true,
prefix: '+',
validate: {
min: 2,
max: 100,
step: 1
}
},
{
type: 'htmlelement',
tag: 'p',
className: 'text-center',
content: '———— X ————'
},
{
type: 'number',
label: 'B',
key: 'b',
input: true,
inputType: 'text',
multiple: true,
prefix: '+',
validate: {
min: 2,
max: 100,
step: 1
}
},
{
type: 'textfield',
label: 'Total',
key: 'total',
input: true,
inputType: 'text',
disabled: true,
calculateValue: {
"*": [
{"_sum": {var: 'data.a'}},
{"_sum": {var: 'data.b'}}
]
}
}
]
});