// 从持仓列表中获取特定币种的持仓
function getPositionBySymbol(positions, symbol) {
    var index = -1;

    if (positions && positions.length > 0) {
        for (var i = 0; i < positions.length; i++) {
            if (positions[i][0].Symbol == symbol) {
                index = i;
                break;
            }
        }
    }