parseOutline.js

var list = [1, 1, 2, 3,3,3, 2, 1, 2, 1];

function parseList(result, node) {
    if (result.length) {
        const parent = result[result.length - 1];
        if (parent.value < node) {
            if (!parent.children)
                parent.children = [];
            parent.children = parseList(parent.children, node)
        } else {
            result.push({
                value: node
            })
        }
    } else {
        result.push({value:node})
    }

    return result;
}

let result = [];

list.forEach(item=>{
    result = parseList(result, item)
}
)

console.log(result)